diff --git a/acinclude.m4 b/acinclude.m4
index 684e7d601..c7d37580c 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -319,6 +319,8 @@ AC_ARG_ENABLE(ebmltest, [  --disable-ebmltest            Do not try to compile a
   else
     if test "x$ebml_include" != "x"; then
       EBML_CFLAGS="-I$ebml_include"
+    else
+      EBML_CFLAGS="-I/usr/include/ebml -I/usr/local/include/ebml"
     fi
     if test "x$ebml_lib" != "x"; then
       EBML_LIBS="-L$ebml_lib"
@@ -438,6 +440,8 @@ AC_ARG_ENABLE(matroskatest, [  --disable-matroskatest        Do not try to compi
   else
     if test "x$matroska_include" != "x"; then
       MATROSKA_CFLAGS="-I$matroska_include"
+    else
+      MATROSKA_CFLAGS="-I/usr/include/matroska -I/usr/local/include/matroska"
     fi
     if test "x$matroska_lib" != "x"; then
       MATROSKA_LIBS="-L$matroska_lib"