diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
index 089a872..1983c81 100644
--- a/src/runtime/runtime.c
+++ b/src/runtime/runtime.c
@@ -547,12 +547,68 @@ static _Bool step(Runtime *runtime, Error *error)
 			return 1;
 
 			case OPCODE_POS:
-			Error_Report(error, 1, "POS not implemented");
-			return 0;
+			{
+				assert(opc == 0);
+
+				if(runtime->frame->used == 0)
+					{
+						Error_Report(error, 1, "Frame doesn't have enough items on the stack to execute POS");
+						return 0;
+					}
+
+				/* Do nothing */
+				return 1;
+			}
 
 			case OPCODE_NEG:
-			Error_Report(error, 1, "NEG not implemented");
-			return 0;
+			{
+				assert(opc == 0);
+
+				if(runtime->frame->used == 0)
+					{
+						Error_Report(error, 1, "Frame doesn't have enough items on the stack to execute NEG");
+						return 0;
+					}
+
+				Object *top = Stack_Top(runtime->stack, 0);
+				assert(top != NULL);
+
+				if(!Runtime_Pop(runtime, error, 1))
+					return 0;
+
+				Heap *heap = Runtime_GetHeap(runtime);
+
+				if(Object_IsInt(top))
+					{
+						long long n = Object_ToInt(top, error);
+
+						if(error->occurred)
+							return 0;
+
+						top = Object_FromInt(-n, heap, error);
+					}
+				else if(Object_IsFloat(top))
+					{
+						double f = Object_ToFloat(top, error);
+
+						if(error->occurred)
+							return 0;
+
+						top = Object_FromFloat(-f, heap, error);
+					}
+				else
+					{
+						Error_Report(error, 0, "Negation operand on a non-numeric object");
+						return 0;
+					}
+
+				if(top == NULL)
+					return 0;
+
+				if(!Runtime_Push(runtime, error, top))
+					return 0;
+				return 1;
+			}
 
 			case OPCODE_NOT:
 			{
diff --git a/tests/test.noja b/tests/test.noja
index 53b576c..21a5bed 100644
--- a/tests/test.noja
+++ b/tests/test.noja
@@ -14,8 +14,8 @@
 
 # Test operations on integers.
 {
-	# assert(4 == +4); -------------------- FAILING
-	# assert(0-4 == -4); ------------------ FAILING
+	assert(4 == +4);
+	assert(0-4 == -4);
 	assert(1 + 1 == 2);
 	assert(2 * 3 == 6);
 	assert(6 / 3 == 2);
@@ -30,8 +30,8 @@
 
 # Test operations on floats.
 {
-	# assert(4.0 == +4.0); # -------------------- FAILING
-	# assert(0-4.0 == -4.0); # ------------------ FAILING
+	assert(4.0 == +4.0);
+	assert(0-4.0 == -4.0);
 	assert(1.0 + 1.0 == 2.0);
 	assert(2.0 * 3.0 == 6.0);
 	assert(6.0 / 3.0 == 2.0);