diff --git a/.travis.yml b/.travis.yml
index 8a9db40..315b140 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -75,4 +75,5 @@ script:
 
 before_install:
   - export PATH=$PATH:$HOME/protobuf/bin
+  - export PROTOC_VERSION=$(cat PROTOC_VERSION)
   - bash install_protobuf.sh
diff --git a/PROTOC_VERSION b/PROTOC_VERSION
new file mode 100644
index 0000000..b7708c4
--- /dev/null
+++ b/PROTOC_VERSION
@@ -0,0 +1 @@
+libprotoc 3.5.1
diff --git a/build.rs b/build.rs
index 8bab568..2a54858 100644
--- a/build.rs
+++ b/build.rs
@@ -15,7 +15,8 @@ fn assert_protobuf_version(version: &str) {
     assert!(version_output.status.success());
     assert_eq!(
         String::from_utf8(version_output.stdout).unwrap().trim(),
-        version
+        version.to_string().trim(),
+        "protoc version must be 3.5.1"
     );
 }
 
@@ -32,7 +33,7 @@ fn build_protobuf(out_dir: &str, input: &[&str], includes: &[&str]) {
 
 #[cfg(feature = "serialization-protobuf")]
 fn build_protobuf_schemata() {
-    assert_protobuf_version("libprotoc 3.5.1");
+    assert_protobuf_version(env!("PROTOC_VERSION"));
     build_protobuf("src/proto", &["protobuf/proof.proto"], &[]);
 }
 
diff --git a/install_protobuf.sh b/install_protobuf.sh
index 0a1432a..8e4dd9f 100644
--- a/install_protobuf.sh
+++ b/install_protobuf.sh
@@ -2,11 +2,11 @@
 set -e
 
 check_protoc_version () {
-    version="libprotoc $1"
-    PROTOC="$HOME/protobuf/bin/protoc"
+    PROTOC_VERSION=$(cat PROTOC_VERSION)
+    PROTOC="protoc"
     if [ -f $PROTOC ]; then
         this_version=`$PROTOC --version`
-        return `[ "$version" = "$this_version" ]`
+        return `[ "$PROTOC_VERSION" = "$this_version" ]`
     else
         return 1
     fi