diff --git a/tools/bufr_split_by_rdbSubtype.c b/tools/bufr_split_by_rdbSubtype.c
index 253a109e7..0b74daa8f 100644
--- a/tools/bufr_split_by_rdbSubtype.c
+++ b/tools/bufr_split_by_rdbSubtype.c
@@ -135,7 +135,7 @@ static int split_file_by_subtype(FILE* in, const char* filename, unsigned long *
             if (verbose) {
                 if (!file_exists(ofilename)) printf("Writing output to %s\n", ofilename);
             }
-            out=fopen(ofilename,"a");
+            out=fopen(ofilename,"ab");
             if (!out) {
                 fprintf(stderr,"ERROR: Failed to open output file '%s'\n", ofilename);
                 perror(ofilename);
@@ -183,7 +183,7 @@ int main(int argc,char* argv[])
             return 1;
         }
     }
-    infh=fopen(filename,"r");
+    infh=fopen(filename,"rb");
     if (!infh) {
         perror(filename);
         return 1;
diff --git a/tools/codes_count.c b/tools/codes_count.c
index 3b09553f3..67a61db02 100644
--- a/tools/codes_count.c
+++ b/tools/codes_count.c
@@ -91,7 +91,7 @@ int main(int argc,char* argv[])
         if (strcmp(filename,"-")==0)
             infh=stdin;
         else
-            infh=fopen(filename,"r");
+            infh=fopen(filename,"rb");
         if (!infh) {
             perror(filename);
             exit(1);
diff --git a/tools/codes_split_file.c b/tools/codes_split_file.c
index daa9879de..8b2973379 100644
--- a/tools/codes_split_file.c
+++ b/tools/codes_split_file.c
@@ -127,7 +127,7 @@ int main(int argc,char* argv[])
             return 1;
         }
     }
-    infh=fopen(filename,"r");
+    infh=fopen(filename,"rb");
     if (!infh) {
         perror(filename);
         return 1;