diff --git a/sdl.m4 b/sdl.m4
index a5db82d32..0928a9ddf 100644
--- a/sdl.m4
+++ b/sdl.m4
@@ -20,19 +20,21 @@ AC_ARG_ENABLE(sdltest, [  --disable-sdltest       Do not try to compile and run
 		    , enable_sdltest=yes)
 
   if test x$sdl_exec_prefix != x ; then
-     sdl_args="$sdl_args --exec-prefix=$sdl_exec_prefix"
-     if test x${SDL_CONFIG+set} != xset ; then
-        SDL_CONFIG=$sdl_exec_prefix/bin/sdl-config
-     fi
+    sdl_args="$sdl_args --exec-prefix=$sdl_exec_prefix"
+    if test x${SDL_CONFIG+set} != xset ; then
+      SDL_CONFIG=$sdl_exec_prefix/bin/sdl-config
+    fi
   fi
   if test x$sdl_prefix != x ; then
-     sdl_args="$sdl_args --prefix=$sdl_prefix"
-     if test x${SDL_CONFIG+set} != xset ; then
-        SDL_CONFIG=$sdl_prefix/bin/sdl-config
-     fi
+    sdl_args="$sdl_args --prefix=$sdl_prefix"
+    if test x${SDL_CONFIG+set} != xset ; then
+      SDL_CONFIG=$sdl_prefix/bin/sdl-config
+    fi
   fi
 
-  PATH="$prefix/bin:$prefix/usr/bin:$PATH"
+  if test "x$prefix" != xNONE; then
+    PATH="$prefix/bin:$prefix/usr/bin:$PATH"
+  fi
   AC_PATH_PROG(SDL_CONFIG, sdl-config, no, [$PATH])
   min_sdl_version=ifelse([$1], ,0.11.0,$1)
   AC_MSG_CHECKING(for SDL - version >= $min_sdl_version)
diff --git a/test/acinclude.m4 b/test/acinclude.m4
index a5db82d32..b6df43f08 100644
--- a/test/acinclude.m4
+++ b/test/acinclude.m4
@@ -20,19 +20,21 @@ AC_ARG_ENABLE(sdltest, [  --disable-sdltest       Do not try to compile and run
 		    , enable_sdltest=yes)
 
   if test x$sdl_exec_prefix != x ; then
-     sdl_args="$sdl_args --exec-prefix=$sdl_exec_prefix"
-     if test x${SDL_CONFIG+set} != xset ; then
-        SDL_CONFIG=$sdl_exec_prefix/bin/sdl-config
-     fi
+    sdl_args="$sdl_args --exec-prefix=$sdl_exec_prefix"
+    if test x${SDL_CONFIG+set} != xset ; then
+       SDL_CONFIG=$sdl_exec_prefix/bin/sdl-config
+    fi
   fi
   if test x$sdl_prefix != x ; then
-     sdl_args="$sdl_args --prefix=$sdl_prefix"
-     if test x${SDL_CONFIG+set} != xset ; then
-        SDL_CONFIG=$sdl_prefix/bin/sdl-config
-     fi
+    sdl_args="$sdl_args --prefix=$sdl_prefix"
+    if test x${SDL_CONFIG+set} != xset ; then
+       SDL_CONFIG=$sdl_prefix/bin/sdl-config
+    fi
   fi
 
-  PATH="$prefix/bin:$prefix/usr/bin:$PATH"
+  if test "x$prefix" != xNONE; then
+    PATH="$prefix/bin:$prefix/usr/bin:$PATH"
+  fi
   AC_PATH_PROG(SDL_CONFIG, sdl-config, no, [$PATH])
   min_sdl_version=ifelse([$1], ,0.11.0,$1)
   AC_MSG_CHECKING(for SDL - version >= $min_sdl_version)