diff --git a/lispBM/lispBM/include/eval_cps.h b/lispBM/lispBM/include/eval_cps.h
index 55e5c15e..3f828fff 100644
--- a/lispBM/lispBM/include/eval_cps.h
+++ b/lispBM/lispBM/include/eval_cps.h
@@ -147,7 +147,7 @@ extern uint32_t lbm_get_eval_state(void);
  *  report an error message to the programmer in case
  *  the extension is used incorrectly.
  *
- *  The error string can be allocates in lbm_memory
+ *  The error string can be allocated in lbm_memory
  *  and will in that case be freed when the context
  *  that errored is removed.
  * \param error_str
diff --git a/lispBM/lispBM/include/lbm_memory.h b/lispBM/lispBM/include/lbm_memory.h
index e20682b6..baca8e00 100644
--- a/lispBM/lispBM/include/lbm_memory.h
+++ b/lispBM/lispBM/include/lbm_memory.h
@@ -89,6 +89,9 @@
 #define LBM_MEMORY_SIZE_2K LBM_MEMORY_SIZE_64BYTES_TIMES_X(32)
 #define LBM_MEMORY_SIZE_4K LBM_MEMORY_SIZE_64BYTES_TIMES_X(64)
 #define LBM_MEMORY_SIZE_8K LBM_MEMORY_SIZE_64BYTES_TIMES_X(128)
+#define LBM_MEMORY_SIZE_10K LBM_MEMORY_SIZE_64BYTES_TIMES_X(160)
+#define LBM_MEMORY_SIZE_12K LBM_MEMORY_SIZE_64BYTES_TIMES_X(192)
+#define LBM_MEMORY_SIZE_14K LBM_MEMORY_SIZE_64BYTES_TIMES_X(224)
 #define LBM_MEMORY_SIZE_16K LBM_MEMORY_SIZE_64BYTES_TIMES_X(256)
 #define LBM_MEMORY_SIZE_32K LBM_MEMORY_SIZE_64BYTES_TIMES_X(512)
 #define LBM_MEMORY_SIZE_1M LBM_MEMORY_SIZE_64BYTES_TIMES_X(16384)
@@ -98,6 +101,9 @@
 #define LBM_MEMORY_BITMAP_SIZE_2K  LBM_MEMORY_BITMAP_SIZE(32)
 #define LBM_MEMORY_BITMAP_SIZE_4K  LBM_MEMORY_BITMAP_SIZE(64)
 #define LBM_MEMORY_BITMAP_SIZE_8K  LBM_MEMORY_BITMAP_SIZE(128)
+#define LBM_MEMORY_BITMAP_SIZE_10K LBM_MEMORY_BITMAP_SIZE(160)
+#define LBM_MEMORY_BITMAP_SIZE_12K LBM_MEMORY_BITMAP_SIZE(192)
+#define LBM_MEMORY_BITMAP_SIZE_14K LBM_MEMORY_BITMAP_SIZE(224)
 #define LBM_MEMORY_BITMAP_SIZE_16K LBM_MEMORY_BITMAP_SIZE(256)
 #define LBM_MEMORY_BITMAP_SIZE_32K LBM_MEMORY_BITMAP_SIZE(512)
 #define LBM_MEMORY_BITMAP_SIZE_1M  LBM_MEMORY_BITMAP_SIZE(16384)
diff --git a/lispBM/lispBM/include/symrepr.h b/lispBM/lispBM/include/symrepr.h
index e4d00eec..726c1d6a 100644
--- a/lispBM/lispBM/include/symrepr.h
+++ b/lispBM/lispBM/include/symrepr.h
@@ -268,8 +268,11 @@ extern int lbm_get_num_variables(void);
 
 /**
  *
- * \return The amount of space occupied by the symbol table in bytes.
+ * \return The total amount of space occupied by the symbol table in bytes.
  */
 extern lbm_uint lbm_get_symbol_table_size(void);
-
+/**
+ * \return The size in bytes of all symbol strings stored in the symbol table.
+ */
+extern lbm_uint lbm_get_symbol_table_size_names(void);
 #endif
diff --git a/lispBM/lispBM/repl/repl.c b/lispBM/lispBM/repl/repl.c
index f7aab4be..31952799 100644
--- a/lispBM/lispBM/repl/repl.c
+++ b/lispBM/lispBM/repl/repl.c
@@ -1,5 +1,5 @@
 /*
-    Copyright 2018, 2021 Joel Svensson  svenssonjoel@yahoo.se
+    Copyright 2018, 2021, 2022 Joel Svensson  svenssonjoel@yahoo.se
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -587,6 +587,7 @@ int main(int argc, char **argv) {
       printf("Memory free: %"PRI_UINT" Words\n", lbm_memory_num_free());
       printf("Allocated arrays: %"PRI_UINT"\n", heap_state.num_alloc_arrays);
       printf("Symbol table size: %"PRI_UINT" Bytes\n", lbm_get_symbol_table_size());
+      printf("Symbol names size: %"PRI_UINT" Bytes\n", lbm_get_symbol_table_size_names());
       free(str);
     }  else if (strncmp(str, ":env", 4) == 0) {
       lbm_value curr = *lbm_get_env_ptr();
diff --git a/lispBM/lispBM/src/extensions.c b/lispBM/lispBM/src/extensions.c
index 2b0bf3b4..083f9865 100644
--- a/lispBM/lispBM/src/extensions.c
+++ b/lispBM/lispBM/src/extensions.c
@@ -24,8 +24,8 @@
 
 #include "extensions.h"
 
-static int ext_offset = EXTENSION_SYMBOLS_START;
-static int ext_max    = -1;
+static lbm_uint ext_offset = EXTENSION_SYMBOLS_START;
+static lbm_uint ext_max    = 0;
 static extension_fptr *extension_table = NULL;
 
 int lbm_extensions_init(extension_fptr *extension_storage, int extension_storage_size) {
@@ -34,35 +34,39 @@ int lbm_extensions_init(extension_fptr *extension_storage, int extension_storage
   extension_table = extension_storage;
   memset(extension_table, 0, sizeof(extension_fptr) * (unsigned int)extension_storage_size);
 
-  ext_max = extension_storage_size;
+  ext_max = (lbm_uint)extension_storage_size;
 
   return 1;
 }
 
 extension_fptr lbm_get_extension(lbm_uint sym) {
-  int ext_next = (int)sym - ext_offset;
-
-  if (ext_next < 0 || ext_next > ext_max) {
+  lbm_uint ext_next = sym - ext_offset;
+  if (ext_next >= ext_max) {
     return NULL;
   }
-
   return extension_table[ext_next];
 }
 
 bool lbm_add_extension(char *sym_str, extension_fptr ext) {
   lbm_value symbol;
-  int res = lbm_add_extension_symbol_const(sym_str, &symbol);
 
-  if (!res) return false;
+  lbm_uint ext_ix = 0;
 
-  int ext_next = (int)symbol - ext_offset;
-
-  if (ext_next < 0 || ext_next > ext_max) {
-    return false;
+  if (lbm_get_symbol_by_name(sym_str, &symbol)) {
+    // symbol already exists and may or may not be an extension.
+    if (lbm_is_extension(symbol)) {
+      ext_ix = lbm_dec_sym(symbol) - ext_offset;
+    } else return false;
+  } else {
+    int res = lbm_add_extension_symbol_const(sym_str, &symbol);
+    if (!res) return false;
+    ext_ix = symbol - ext_offset;
   }
 
-  extension_table[ext_next] = ext;
-
+  if (ext_ix >= ext_max) {
+      return false;
+  }
+  extension_table[ext_ix] = ext;
   return true;
 }
 
diff --git a/lispBM/lispBM/src/symrepr.c b/lispBM/lispBM/src/symrepr.c
index e852aa3c..a0a8d5ed 100644
--- a/lispBM/lispBM/src/symrepr.c
+++ b/lispBM/lispBM/src/symrepr.c
@@ -207,11 +207,16 @@ static lbm_uint next_symbol_id = RUNTIME_SYMBOLS_START;
 static lbm_uint next_extension_symbol_id = EXTENSION_SYMBOLS_START;
 static lbm_uint next_variable_symbol_id = VARIABLE_SYMBOLS_START;
 
+static lbm_uint symbol_table_size_list = 0;
+static lbm_uint symbol_table_size_strings = 0;
+
 int lbm_symrepr_init(void) {
   symlist = NULL;
   next_symbol_id = RUNTIME_SYMBOLS_START;
   next_extension_symbol_id = EXTENSION_SYMBOLS_START;
   next_variable_symbol_id = VARIABLE_SYMBOLS_START;
+  symbol_table_size_list = 0;
+  symbol_table_size_strings = 0;
   return 1;
 }
 
@@ -283,18 +288,24 @@ int lbm_add_symbol(char *name, lbm_uint* id) {
     return 0;
   }
 
-  char *symbol_name_storage = NULL;;
+  char *symbol_name_storage = NULL;
+  lbm_uint alloc_size;
   if (n % sizeof(lbm_uint) == 0) {
-    symbol_name_storage = (char *)lbm_memory_allocate(n/sizeof(lbm_uint));
+    alloc_size = n/(sizeof(lbm_uint));
   } else {
-    symbol_name_storage = (char *)lbm_memory_allocate((n/sizeof(lbm_uint)) + 1);
+    alloc_size = (n/(sizeof(lbm_uint))) + 1;
   }
 
+  symbol_name_storage = (char *)lbm_memory_allocate(alloc_size);
+
   if (symbol_name_storage == NULL) {
     lbm_memory_free(m);
     return 0;
   }
 
+  symbol_table_size_list += 3;
+  symbol_table_size_strings += alloc_size;
+
   strcpy(symbol_name_storage, name);
 
   m[NAME] = (lbm_uint)symbol_name_storage;
@@ -325,18 +336,24 @@ int lbm_add_variable_symbol(char *name, lbm_uint* id) {
     return 0;
   }
 
-  char *symbol_name_storage = NULL;;
+  char *symbol_name_storage = NULL;
+  lbm_uint alloc_size;
   if (n % sizeof(lbm_uint) == 0) {
-    symbol_name_storage = (char *)lbm_memory_allocate(n/sizeof(lbm_uint));
+    alloc_size = n/(sizeof(lbm_uint));
   } else {
-    symbol_name_storage = (char *)lbm_memory_allocate((n/sizeof(lbm_uint)) + 1);
+    alloc_size = (n/(sizeof(lbm_uint))) + 1;
   }
 
+  symbol_name_storage = (char *)lbm_memory_allocate(alloc_size);
+
   if (symbol_name_storage == NULL) {
     lbm_memory_free(m);
     return 0;
   }
 
+  symbol_table_size_list += 3;
+  symbol_table_size_strings += alloc_size;
+
   strcpy(symbol_name_storage, name);
 
   m[NAME] = (lbm_uint)symbol_name_storage;
@@ -363,6 +380,8 @@ int lbm_add_symbol_const(char *name, lbm_uint* id) {
     return 0;
   }
 
+  symbol_table_size_list += 3;
+
   m[NAME] = (lbm_uint)name;
 
   if (symlist == NULL) {
@@ -387,6 +406,8 @@ int lbm_add_extension_symbol_const(char *name, lbm_uint* id) {
     return 0;
   }
 
+  symbol_table_size_list += 3;
+
   m[NAME] = (lbm_uint)name;
 
   if (symlist == NULL) {
@@ -403,21 +424,13 @@ int lbm_add_extension_symbol_const(char *name, lbm_uint* id) {
 
 
 lbm_uint lbm_get_symbol_table_size(void) {
-
-  lbm_uint n = 0;
-  lbm_uint *curr = symlist;
-
-  while (curr) {
-    // up to 3 extra bytes are used for string storage if length is not multiple of 4
-    size_t s = strlen((char *)curr[NAME]);
-    s ++;
-    n += s % sizeof(lbm_uint);
-    n += 12; // sizeof the node in the linked list
-    curr = (lbm_uint *)curr[NEXT];
-  }
-  return n;
+  return (symbol_table_size_list +
+          symbol_table_size_strings) * sizeof(lbm_uint);
 }
 
+lbm_uint lbm_get_symbol_table_size_names(void) {
+  return symbol_table_size_strings * sizeof(lbm_uint);
+}
 
 int lbm_get_num_variables(void) {
   return (int)next_variable_symbol_id - VARIABLE_SYMBOLS_START;
diff --git a/lispBM/lispBM/tests/test_lisp_code_cps.c b/lispBM/lispBM/tests/test_lisp_code_cps.c
index 056cdcc2..ca35c857 100644
--- a/lispBM/lispBM/tests/test_lisp_code_cps.c
+++ b/lispBM/lispBM/tests/test_lisp_code_cps.c
@@ -260,14 +260,14 @@ int main(int argc, char **argv) {
     return 0;
   }
 
-  lbm_uint *memory = malloc(sizeof(lbm_uint) * LBM_MEMORY_SIZE_32K);
+  lbm_uint *memory = malloc(sizeof(lbm_uint) * LBM_MEMORY_SIZE_12K);
   if (memory == NULL) return 0;
-  lbm_uint *bitmap = malloc(sizeof(lbm_uint) * LBM_MEMORY_BITMAP_SIZE_32K);
+  lbm_uint *bitmap = malloc(sizeof(lbm_uint) * LBM_MEMORY_BITMAP_SIZE_12K);
   if (bitmap == NULL) return 0;
 
 
-  res = lbm_memory_init(memory, LBM_MEMORY_SIZE_16K,
-                        bitmap, LBM_MEMORY_BITMAP_SIZE_16K);
+  res = lbm_memory_init(memory, LBM_MEMORY_SIZE_12K,
+                        bitmap, LBM_MEMORY_BITMAP_SIZE_12K);
   if (res)
     printf("Memory initialized.\n");
   else {