diff --git a/CMakeLists.txt b/CMakeLists.txt
index 82fda48..820958c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,11 +14,11 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "bin")
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 set(HASH_MAP_TEST_SOURCES src/debug.c src/hash_map.c src/seconds.c src/tests/hash_map_test.c)
-set(INTERPRET_TEST_SOURCES src/debug.c src/hash_map.c src/memory.c src/seconds.c src/types.c
-  src/vm/instructions.c src/vm/opcodes.c src/vm/stack.c src/vm/vm.c src/tests/interpret_test.c)
+set(INTERPRET_TEST_SOURCES src/debug.c src/hash_map.c src/memory.c src/seconds.c src/stack.c
+  src/types.c src/vm/instructions.c src/vm/opcodes.c src/vm/vm.c src/tests/interpret_test.c)
 set(OBJECT_TEST_SOURCES src/debug.c src/memory.c src/seconds.c src/types.c src/tests/object_test.c)
-set(STACK_TEST_SOURCES src/debug.c src/hash_map.c src/memory.c src/seconds.c src/types.c
-  src/vm/instructions.c src/vm/stack.c src/tests/stack_test.c)
+set(STACK_TEST_SOURCES src/debug.c src/hash_map.c src/memory.c src/seconds.c src/stack.c
+  src/types.c src/vm/instructions.c src/tests/stack_test.c)
 set(UNIT_TESTS_SOURCES src/debug.c src/memory.c src/seconds.c src/types.c src/tests/unit_tests.c)
 
 if(MSVC)
diff --git a/include/memory.h b/include/memory.h
index a1ce569..2c1e8d9 100644
--- a/include/memory.h
+++ b/include/memory.h
@@ -29,7 +29,7 @@
 #define MEMORY_H
 
 #include "types.h"
-#include "vm/stack.h"
+#include "stack.h"
 
 // Initial free store capacity
 static const size_t INITIAL_STORE_CAPACITY = 128;
diff --git a/include/vm/stack.h b/include/stack.h
similarity index 89%
rename from include/vm/stack.h
rename to include/stack.h
index d395ae1..62657db 100644
--- a/include/vm/stack.h
+++ b/include/stack.h
@@ -31,25 +31,25 @@
 #include <stddef.h> // NULL
 #include "types.h"
 
-#define MAX_STACK_CAPACITY ((size_t)64)
+#define MAX_STACK_CAPACITY ((size_t)128)
 
-typedef struct vm_stack
+typedef struct stack
 {
-  int top;
+  int16_t top;
   size_t count;
-  Object* objects[MAX_STACK_CAPACITY];
+  void* objects[MAX_STACK_CAPACITY];
 } Stack;
 
 // Initializes stack
 void init_stack(Stack* stack);
 
 // Returns object at top of stack without removal
-Object* peek(const Stack* stack);
+void* peek(const Stack* stack);
 
 // Returns and removes object at top of stack
-Object* pop(Stack* stack);
+void* pop(Stack* stack);
 
 // Pushes new object on top of stack
-void push(Stack* stack, Object* object);
+void push(Stack* stack, void* object);
 
 #endif // STACK_H
diff --git a/include/vm/instructions.h b/include/vm/instructions.h
index 6a08aa8..f70a6aa 100644
--- a/include/vm/instructions.h
+++ b/include/vm/instructions.h
@@ -29,7 +29,7 @@
 #define INSTRUCTIONS_H
 
 #include "hash_map.h"
-#include "vm/stack.h"
+#include "stack.h"
 #include "vm/vm.h"
 
 #define OP_NOOP (void)0
diff --git a/include/vm/vm.h b/include/vm/vm.h
index b15d601..a9c10fd 100644
--- a/include/vm/vm.h
+++ b/include/vm/vm.h
@@ -28,9 +28,9 @@
 #ifndef VM_H
 #define VM_H
 
+#include "stack.h"
 #include "types.h"      // BigNum, Byte
 #include "vm/opcodes.h" // Opcode
-#include "vm/stack.h"   // Stack
 
 #define REGISTER_AMOUNT ((uint8_t)17)
 static const uint8_t REGISTER_EMPTY = 127;
diff --git a/src/compiler.c b/src/compiler.c
index 8abf930..f9915cb 100644
--- a/src/compiler.c
+++ b/src/compiler.c
@@ -124,7 +124,10 @@ void compile(ConcoctNodeTree* tree, ConcoctHashMap* map)
         ic++;
         break;
       case CCT_TOKEN_ADD_ASSIGN:
-        // OP_ADD + OP_ASN
+        vm.instructions[ic] = OP_ADD;
+        ic++;
+        vm.instructions[ic] = OP_ASN;
+        ic++;
         break;
       case CCT_TOKEN_AND:
         vm.instructions[ic] = OP_AND;
@@ -273,6 +276,10 @@ void compile(ConcoctNodeTree* tree, ConcoctHashMap* map)
         vm.instructions[ic] = OP_TRU;
         ic++;
         break;
+      case CCT_TOKEN_UNARY_MINUS:
+        vm.instructions[ic] = OP_NEG;
+        ic++;
+        break;
       default:
         fprintf(stderr, "Unable to handle token: %s\n", cct_token_type_to_string(current->token.type));
         break;
diff --git a/src/lexer.c b/src/lexer.c
index 9a7a0c6..932ba54 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -208,7 +208,7 @@ ConcoctToken cct_next_token(ConcoctLexer* lexer)
     if(cct_hash_map_has_key(lexer->keyword_map, lexer->token_text))
     {
       void* void_pointer = cct_hash_map_get(lexer->keyword_map, lexer->token_text);
-      int* pointer_to_type = (int*) (&void_pointer);
+      const int* pointer_to_type = (int *)(&void_pointer);
       type = *pointer_to_type;
     }
     else
diff --git a/src/parser.c b/src/parser.c
index 8fa6b8d..891be2c 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -219,7 +219,9 @@ ConcoctNode* cct_parse_unary_expr(ConcoctParser* parser)
     case CCT_TOKEN_SUB:
       // Change the token type so the compiler knows which operation it is
       parser->current_token.type = CCT_TOKEN_UNARY_MINUS;
+      goto TOK_ADD_LBL; // portable way to handle intentional fallthrough and silence -Wimplicit-fallthrough
     case CCT_TOKEN_ADD:
+      TOK_ADD_LBL:
     case CCT_TOKEN_NOT:
     case CCT_TOKEN_INC:
     case CCT_TOKEN_DEC:
diff --git a/src/vm/stack.c b/src/stack.c
similarity index 93%
rename from src/vm/stack.c
rename to src/stack.c
index e2837ba..1921fad 100644
--- a/src/vm/stack.c
+++ b/src/stack.c
@@ -25,10 +25,10 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <stdio.h>    // fprintf(), stderr
-#include <stdlib.h>   // EXIT_FAILURE
+#include <stdio.h>  // fprintf(), stderr
+#include <stdlib.h> // EXIT_FAILURE
 #include "debug.h"
-#include "vm/stack.h"
+#include "stack.h"
 
 void init_stack(Stack* stack)
 {
@@ -40,7 +40,7 @@ void init_stack(Stack* stack)
 }
 
 // Returns object at top of stack without removal
-Object* peek(const Stack* stack)
+void* peek(const Stack* stack)
 {
   if(stack->top == -1)
   {
@@ -54,7 +54,7 @@ Object* peek(const Stack* stack)
 }
 
 // Returns and removes object at top of stack
-Object* pop(Stack* stack)
+void* pop(Stack* stack)
 {
   if(stack->top == -1)
   {
@@ -68,7 +68,7 @@ Object* pop(Stack* stack)
 }
 
 // Pushes new object on top of stack
-void push(Stack* stack, Object* object)
+void push(Stack* stack, void* object)
 {
   if(stack->top >= ((int)MAX_STACK_CAPACITY - 1))
   {
diff --git a/src/tests/stack_test.c b/src/tests/stack_test.c
index 7d56cca..7034e50 100644
--- a/src/tests/stack_test.c
+++ b/src/tests/stack_test.c
@@ -28,9 +28,9 @@
 #include <stdio.h>
 #include "debug.h"
 #include "memory.h"
+#include "stack.h"
 #include "types.h"
 #include "vm/instructions.h"
-#include "vm/stack.h"
 
 int main()
 {
diff --git a/src/vm/instructions.c b/src/vm/instructions.c
index bcc82e6..ceb77ed 100644
--- a/src/vm/instructions.c
+++ b/src/vm/instructions.c
@@ -207,7 +207,7 @@ RunCode op_asn(Stack* stack, ConcoctHashMap* map)
     fprintf(stderr, "Value is NULL during ASN operation.\n");
     return RUN_ERROR;
   }
-  cct_hash_map_set(map, key->value.strobj.strval, (Object *)val);
+  cct_hash_map_set(map, key->value.strobj.strval, val);
   if(debug_mode)
     print_object_value((Object *)cct_hash_map_get(map, key->value.strobj.strval));
   key->is_flagged = true; // throw away the key since we have it in the map