diff --git a/.travis.yml b/.travis.yml
index dd619c945d4..889d1d4ef76 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -34,6 +34,7 @@ matrix:
         SCCACHE_ERROR_LOG=/tmp/sccache.log
         MACOSX_DEPLOYMENT_TARGET=10.7
         NO_LLVM_ASSERTIONS=1
+        NO_DEBUG_ASSERTIONS=1
       os: osx
       osx_image: xcode7
       if: branch = auto
@@ -54,6 +55,7 @@ matrix:
         MACOSX_DEPLOYMENT_TARGET=10.8
         MACOSX_STD_DEPLOYMENT_TARGET=10.7
         NO_LLVM_ASSERTIONS=1
+        NO_DEBUG_ASSERTIONS=1
       os: osx
       osx_image: xcode8.2
       if: branch = auto
@@ -67,6 +69,7 @@ matrix:
         MACOSX_DEPLOYMENT_TARGET=10.8
         MACOSX_STD_DEPLOYMENT_TARGET=10.7
         NO_LLVM_ASSERTIONS=1
+        NO_DEBUG_ASSERTIONS=1
       os: osx
       osx_image: xcode8.2
       if: branch = auto
@@ -86,6 +89,7 @@ matrix:
         SCCACHE_ERROR_LOG=/tmp/sccache.log
         MACOSX_DEPLOYMENT_TARGET=10.7
         NO_LLVM_ASSERTIONS=1
+        NO_DEBUG_ASSERTIONS=1
       os: osx
       osx_image: xcode7
       if: branch = auto
@@ -99,6 +103,7 @@ matrix:
         SCCACHE_ERROR_LOG=/tmp/sccache.log
         MACOSX_DEPLOYMENT_TARGET=10.7
         NO_LLVM_ASSERTIONS=1
+        NO_DEBUG_ASSERTIONS=1
       os: osx
       osx_image: xcode7
       if: branch = auto
diff --git a/src/ci/run.sh b/src/ci/run.sh
index 39fb4e44078..b4fa033c4a6 100755
--- a/src/ci/run.sh
+++ b/src/ci/run.sh
@@ -52,7 +52,11 @@ if [ "$DEPLOY$DEPLOY_ALT" != "" ]; then
     RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-llvm-assertions"
   fi
 else
-  RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-debug-assertions"
+  # We almost always want debug assertions enabled, but sometimes this takes too
+  # long for too little benefit, so we just turn them off.
+  if [ "$NO_DEBUG_ASSERTIONS" = "" ]; then
+    RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-debug-assertions"
+  fi
 
   # In general we always want to run tests with LLVM assertions enabled, but not
   # all platforms currently support that, so we have an option to disable.