diff --git a/cmake/modules/FindLEX.cmake b/cmake/modules/FindLEX.cmake
index 0008bc43dd..20caa096c8 100644
--- a/cmake/modules/FindLEX.cmake
+++ b/cmake/modules/FindLEX.cmake
@@ -34,7 +34,7 @@ MACRO(ADD_LEX_FILES _source _generated)
 
       ADD_CUSTOM_COMMAND(
         OUTPUT ${_outc} ${_outh}
-        COMMAND ${LEX_EXECUTABLE} -o${_outc} --header-file=${_outh} ${_in}
+        COMMAND ${LEX_EXECUTABLE} $<$<OR:$<CONFIG:Debug>,$<CONFIG:RelWithDebInfo>>:--debug> -o${_outc} --header-file=${_outh} ${_in}
         DEPENDS ${_in}
       )
       LIST(APPEND ${_source} ${_in})
diff --git a/epan/dfilter/dfilter.c b/epan/dfilter/dfilter.c
index 934a8f95f2..6eab71797c 100644
--- a/epan/dfilter/dfilter.c
+++ b/epan/dfilter/dfilter.c
@@ -425,16 +425,16 @@ dfilter_compile_real(const gchar *text, dfilter_t **dfp,
 
 	df_yyset_extra(&state, scanner);
 
+#ifdef NDEBUG
+	if (flags & DF_DEBUG_FLEX || flags & DF_DEBUG_LEMON) {
+		ws_message("Compile Wireshark without NDEBUG to enable Flex and/or Lemon debug traces");
+	}
+#else
 	/* Enable/disable debugging for Flex. */
 	df_yyset_debug(flags & DF_DEBUG_FLEX, scanner);
 
-#ifndef NDEBUG
 	/* Enable/disable debugging for Lemon. */
 	DfilterTrace(flags & DF_DEBUG_LEMON ? stderr : NULL, "lemon> ");
-#else
-	if (flags & DF_DEBUG_LEMON) {
-		ws_message("Compile Wireshark without NDEBUG to enable Lemon debug traces");
-	}
 #endif
 
 	while (1) {
diff --git a/epan/dfilter/scanner.l b/epan/dfilter/scanner.l
index 04c57de19a..cda287ef54 100644
--- a/epan/dfilter/scanner.l
+++ b/epan/dfilter/scanner.l
@@ -20,11 +20,6 @@
  */
 %option warn
 
-/*
- * Generate debug code (output is off by default for reentrant scanners).
- */
-%option debug
-
 /*
  * We want a reentrant scanner.
  */