diff --git a/.travis.yml b/.travis.yml
index 68a5cda..caeab6e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,7 +25,9 @@ script:
 # Make sure nightly targets are not broken.
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --tests --manifest-path=fuzz/Cargo.toml; fi
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --benches --manifest-path=benches/Cargo.toml; fi
-- ./test.sh
+# Run tests in the release mode since some of the tests from the spec
+# perfrom reaaally bad in the debug mode.
+- CARGOFLAGS=--release ./test.sh
 - ./doc.sh
 after_success: |
   # Build documentation and deploy it to github pages.
diff --git a/src/runner.rs b/src/runner.rs
index 51c9661..719d607 100644
--- a/src/runner.rs
+++ b/src/runner.rs
@@ -19,9 +19,9 @@ use memory_units::Pages;
 use nan_preserving_float::{F32, F64};
 
 /// Maximum number of entries in value stack.
-pub const DEFAULT_VALUE_STACK_LIMIT: usize = 16384;
+pub const DEFAULT_VALUE_STACK_LIMIT: usize = 4 * 1024 * 1024;
 /// Maximum number of entries in frame stack.
-pub const DEFAULT_FRAME_STACK_LIMIT: usize = 16384;
+pub const DEFAULT_FRAME_STACK_LIMIT: usize = 4 * 1024 * 1024;
 
 /// Function interpreter.
 pub struct Interpreter<'a, E: Externals + 'a> {
diff --git a/test.sh b/test.sh
index 3cef9ad..89da0a1 100755
--- a/test.sh
+++ b/test.sh
@@ -1,9 +1,9 @@
 #!/usr/bin/env bash
 
-set -eux
+set -ex
 
 cd $(dirname $0)
 
-time cargo test
+time cargo test $CARGOFLAGS
 
 cd -