diff --git a/ETL/m4/subs.m4 b/ETL/m4/subs.m4
index 6204a48d0..1723159b4 100644
--- a/ETL/m4/subs.m4
+++ b/ETL/m4/subs.m4
@@ -82,8 +82,8 @@ AC_DEFUN([AC_ARG_DEBUG],
 		;;
 		no|*)
 			debug_flags="-DNDEBUG"
-			CXXFLAGS="`echo $CXXFLAGS | sed 's:-g[[a-z-]]*\s::g' | sed 's:-g[[a-z-]]*$::'` $debug_flags"
-			CFLAGS="`echo $CFLAGS | sed 's:-g[[a-z-]]*\s::g' | sed 's:-g[[a-z-]]*$::'` $debug_flags"
+			CXXFLAGS="`echo $CXXFLAGS | sed 's:^-g[[^ $]]*::g' | sed 's:\s-g[[^ $]]*::g'` $debug_flags"
+			CFLAGS="`echo $CFLAGS | sed 's:^-g[[^ $]]*::g' | sed 's:\s-g[[^ $]]*::g'` $debug_flags"
 		;;
 	esac
 
diff --git a/synfig-core/m4/subs.m4 b/synfig-core/m4/subs.m4
index a20fc6689..47bff2b18 100644
--- a/synfig-core/m4/subs.m4
+++ b/synfig-core/m4/subs.m4
@@ -85,8 +85,8 @@ AC_DEFUN([AC_ARG_DEBUG],
 		;;
 		no|*)
 			debug_flags="-DNDEBUG"
-			CXXFLAGS="`echo $CXXFLAGS | sed 's:-g[[a-z-]]*\s::g' | sed 's:-g[[a-z-]]*$::'` $debug_flags"
-			CFLAGS="`echo $CFLAGS | sed 's:-g[[a-z-]]*\s::g' | sed 's:-g[[a-z-]]*$::'` $debug_flags"
+			CXXFLAGS="`echo $CXXFLAGS | sed 's:^-g[[^ $]]*::g' | sed 's:\s-g[[^ $]]*::g'` $debug_flags"
+			CFLAGS="`echo $CFLAGS | sed 's:^-g[[^ $]]*::g' | sed 's:\s-g[[^ $]]*::g'` $debug_flags"
 		;;
 	esac
 
diff --git a/synfig-studio/m4/subs.m4 b/synfig-studio/m4/subs.m4
index c529476d5..6c2f1d513 100644
--- a/synfig-studio/m4/subs.m4
+++ b/synfig-studio/m4/subs.m4
@@ -83,8 +83,8 @@ AC_DEFUN([AC_ARG_DEBUG],
 		;;
 		no|*)
 			debug_flags="-DNDEBUG"
-			CXXFLAGS="`echo $CXXFLAGS | sed 's:-g[[a-z-]]*\s::g' | sed 's:-g[[a-z-]]*$::'` $debug_flags"
-			CFLAGS="`echo $CFLAGS | sed 's:-g[[a-z-]]*\s::g' | sed 's:-g[[a-z-]]*$::'` $debug_flags"
+			CXXFLAGS="`echo $CXXFLAGS | sed 's:^-g[[^ $]]*::g' | sed 's:\s-g[[^ $]]*::g'` $debug_flags"
+			CFLAGS="`echo $CFLAGS | sed 's:^-g[[^ $]]*::g' | sed 's:\s-g[[^ $]]*::g'` $debug_flags"
 		;;
 	esac