diff --git a/src/main/java/com/teragrep/pth10/ast/commands/transformstatement/convert/Memk.java b/src/main/java/com/teragrep/pth10/ast/commands/transformstatement/convert/Memk.java
index b2dd1a49b..8d4d05385 100644
--- a/src/main/java/com/teragrep/pth10/ast/commands/transformstatement/convert/Memk.java
+++ b/src/main/java/com/teragrep/pth10/ast/commands/transformstatement/convert/Memk.java
@@ -66,7 +66,7 @@ public String call(String input) throws Exception {
         Matcher m = Pattern.compile("\\d+(.\\d+)?").matcher(input);
 
         if (!m.find()) {
-            throw new RuntimeException(
+            throw new IllegalArgumentException(
                     "Invalid value given for function memk(). Expected: Positive integer or float, with an optional unit k, m or g. Instead got: "
                             + input
             );