diff --git a/SLS_C/src/builtin.c b/SLS_C/src/builtin.c
index 19e7160..630bba6 100644
--- a/SLS_C/src/builtin.c
+++ b/SLS_C/src/builtin.c
@@ -1003,11 +1003,13 @@ Boolean builtin_abs(InterpreterState *interpreter_state) {
 
 Boolean builtin_acos(InterpreterState *interpreter_state) {
     NUMERIC_TYPE;
+    if (af < -1 || af > 1) return FALSE;
     FLOAT_FUNCTION(acos);
 }
 
 Boolean builtin_asin(InterpreterState *interpreter_state) {
     NUMERIC_TYPE;
+    if (af < -1 || af > 1) return FALSE;
     FLOAT_FUNCTION(asin);
 }
 
@@ -1105,11 +1107,13 @@ Boolean builtin_lambda(InterpreterState *interpreter_state) {
 
 Boolean builtin_ln(InterpreterState *interpreter_state) {
     NUMERIC_TYPE;
+    if (af <= 0) return FALSE;
     FLOAT_FUNCTION(log);
 }
 
 Boolean builtin_log(InterpreterState *interpreter_state) {
     NUMERIC_TYPE;
+    if (af <= 0) return FALSE;
     FLOAT_FUNCTION(log10);
 }
 
@@ -1190,6 +1194,7 @@ Boolean builtin_sin(InterpreterState *interpreter_state) {
 
 Boolean builtin_sqrt(InterpreterState *interpreter_state) {
     NUMERIC_TYPE;
+    if (af < 0) return FALSE;
     FLOAT_FUNCTION(sqrt);
 }