--- src/core/org/apache/jmeter/functions/gui/FunctionHelper.java	(Revision 1851852)
+++ src/core/org/apache/jmeter/functions/gui/FunctionHelper.java	(Arbeitskopie)
@@ -22,6 +22,9 @@ 
 import java.awt.FlowLayout;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
 import java.util.Arrays;
 import java.util.List;
 
@@ -251,7 +254,7 @@ 
                 if (!first) {
                     functionCall.append(",");
                 }
-                functionCall.append(arg.getValue().replaceAll(",", "\\\\,"));
+                functionCall.append(escapeCommata(arg.getValue()));
                 first = false;
             }
             functionCall.append(")");
@@ -260,6 +263,41 @@ 
         return functionCall.toString();
     }
 
+    private static final char ANY_NORMAL_CHAR = ' ';
+
+    /**
+     * Escape commata that are in the argument but "outside" of variable replacement structures.
+     *
+     * @param arg string that should be escaped
+     * @return escaped string
+     */
+    private String escapeCommata(String arg) {
+        int level = 0;
+        StringBuilder result = new StringBuilder(arg.length());
+        try (Reader r = new StringReader(arg)) {
+            int c;
+            char lastChar = ANY_NORMAL_CHAR;
+            while ((c = r.read()) != -1) {
+                char nextChar = (char) c;
+                if (lastChar == '\\') {
+                    // do nothing
+                } else if (lastChar == '$' && nextChar == '{') {
+                    level++;
+                } else if (nextChar == '}') {
+                    level--;
+                } else if (nextChar == ',' && level == 0) {
+                    result.append('\\');
+                }
+                lastChar = nextChar;
+                result.append(nextChar);
+            }
+        } catch (IOException e) {
+            log.warn("Can't escape commata in input string: {}", arg, e);
+            return arg;
+        }
+        return result.toString();
+    }
+
     private class HelpListener implements ActionListener {
         @Override
         public void actionPerformed(ActionEvent e) {
--- test/src/org/apache/jmeter/functions/gui/FunctionHelperSpec.groovy	(Revision 1851852)
+++ test/src/org/apache/jmeter/functions/gui/FunctionHelperSpec.groovy	(Arbeitskopie)
@@ -47,6 +47,8 @@ 
           "fname"      | ["a,b,c"]     | "\${fname(a\\,b\\,c)}"
           "fname"      | ["a", "b"]    | "\${fname(a,b)}"
           "fname"      | ["a,b", "c"]  | "\${fname(a\\,b,c)}"
+          "fname"      | ["\${f(a,b)},c,\${g(d,e)}","h"]   | "\${fname(\${f(a,b)}\\,c\\,\${g(d,e)},h)}"
+          "fname"      | ["a,\${f(b,\${g(c,d)},e)},f","h"] | "\${fname(a\\,\${f(b,\${g(c,d)},e)}\\,f,h)}"
     }
 }