diff --git a/src/cairo-type1-subset.c b/src/cairo-type1-subset.c
index a51e34f62..c7ab367e8 100644
--- a/src/cairo-type1-subset.c
+++ b/src/cairo-type1-subset.c
@@ -254,7 +254,7 @@ cairo_type1_font_subset_find_segments (cairo_type1_font_subset_t *font)
 	font->eexec_segment = (char *) p + font->header_segment_size;
 	font->eexec_segment_is_ascii = TRUE;
 	for (i = 0; i < 4; i++) {
-	    if (!isxdigit(font->eexec_segment[i]))
+	    if (!_cairo_isxdigit (font->eexec_segment[i]))
 		font->eexec_segment_is_ascii = FALSE;
 	}
     }
diff --git a/src/cairoint.h b/src/cairoint.h
index 03ca09c10..832d80f3f 100644
--- a/src/cairoint.h
+++ b/src/cairoint.h
@@ -286,6 +286,12 @@ _cairo_isdigit (int c)
     return (c >= '0' && c <= '9');
 }
 
+static inline int cairo_const
+_cairo_isxdigit (int c)
+{
+    return ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'));
+}
+
 static inline int cairo_const
 _cairo_isalpha (int c)
 {