diff --git a/src/ruby/ext/grpc/rb_call.c b/src/ruby/ext/grpc/rb_call.c
index cbea76c3bfd611c0406b451b70de5fec45a19801..43adafb73f9a9a0d7b81e2a99fc73c726c4424f7 100644
--- a/src/ruby/ext/grpc/rb_call.c
+++ b/src/ruby/ext/grpc/rb_call.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -310,15 +310,20 @@ static int grpc_rb_md_ary_fill_hash_cb(VALUE key, VALUE val, VALUE md_ary_obj) {
   grpc_metadata_array *md_ary = NULL;
   long array_length;
   long i;
-
   char *key_str;
+  size_t key_len;
+  char *value_str;
+  size_t value_len;
+
   if (TYPE(key) == T_SYMBOL) {
     key_str = (char *)rb_id2name(SYM2ID(key));
+    key_len = strlen(key_str);
   } else { /* StringValueCStr does all other type exclusions for us */
     key_str = StringValueCStr(key);
+    key_len = RSTRING_LEN(key);
   }
 
-  if (!grpc_header_key_is_legal(key_str)) {
+  if (!grpc_header_key_is_legal(key_str, key_len)) {
     rb_raise(rb_eArgError,
              "'%s' is an invalid header key, must match [a-z0-9-_.]+",
              key_str);
@@ -330,19 +335,36 @@ static int grpc_rb_md_ary_fill_hash_cb(VALUE key, VALUE val, VALUE md_ary_obj) {
                        &grpc_rb_md_ary_data_type, md_ary);
 
   if (TYPE(val) == T_ARRAY) {
-    /* If the value is an array, add capacity for each value in the array */
     array_length = RARRAY_LEN(val);
+    /* If the value is an array, add capacity for each value in the array */
     for (i = 0; i < array_length; i++) {
+      value_str = RSTRING_PTR(rb_ary_entry(val, i));
+      value_len = RSTRING_LEN(rb_ary_entry(val, i));
+      if (!grpc_is_binary_header(key_str, key_len) &&
+          !grpc_header_nonbin_value_is_legal(value_str, value_len)) {
+        // The value has invalid characters
+        rb_raise(rb_eArgError,
+                 "Header value '%s' has invalid characters", value_str);
+        return ST_STOP;
+      }
       md_ary->metadata[md_ary->count].key = key_str;
-      md_ary->metadata[md_ary->count].value = RSTRING_PTR(rb_ary_entry(val, i));
-      md_ary->metadata[md_ary->count].value_length =
-          RSTRING_LEN(rb_ary_entry(val, i));
+      md_ary->metadata[md_ary->count].value = value_str;
+      md_ary->metadata[md_ary->count].value_length = value_len;
       md_ary->count += 1;
     }
   } else {
+    value_str = RSTRING_PTR(val);
+    value_len = RSTRING_LEN(val);
+    if (!grpc_is_binary_header(key_str, key_len) &&
+        !grpc_header_nonbin_value_is_legal(value_str, value_len)) {
+      // The value has invalid characters
+      rb_raise(rb_eArgError,
+               "Header value '%s' has invalid characters", value_str);
+      return ST_STOP;
+    }
     md_ary->metadata[md_ary->count].key = key_str;
-    md_ary->metadata[md_ary->count].value = RSTRING_PTR(val);
-    md_ary->metadata[md_ary->count].value_length = RSTRING_LEN(val);
+    md_ary->metadata[md_ary->count].value = value_str;
+    md_ary->metadata[md_ary->count].value_length = value_len;
     md_ary->count += 1;
   }
 
diff --git a/templates/grpc.gemspec.template b/templates/grpc.gemspec.template
index 5c220052e774cb2315c413336243630eff4ea6bc..8839b9be5544d43f3b1de407121ea0ce432ed622 100644
--- a/templates/grpc.gemspec.template
+++ b/templates/grpc.gemspec.template
@@ -35,7 +35,7 @@
     s.platform      = Gem::Platform::RUBY
 
     s.add_dependency 'google-protobuf', '~> 3.0.0alpha.1.1'
-    s.add_dependency 'googleauth', '~> 0.4'
+    s.add_dependency 'googleauth', '~> 0.5.1'
 
     s.add_development_dependency 'bundler', '~> 1.9'
     s.add_development_dependency 'logging', '~> 2.0'