diff --git a/eth2/state_processing/Cargo.toml b/eth2/state_processing/Cargo.toml
index 1bc7a6c45..a2ae11aa8 100644
--- a/eth2/state_processing/Cargo.toml
+++ b/eth2/state_processing/Cargo.toml
@@ -30,3 +30,6 @@ tree_hash = { path = "../utils/tree_hash" }
 tree_hash_derive = { path = "../utils/tree_hash_derive" }
 types = { path = "../types" }
 rayon = "1.0"
+
+[features]
+fake_crypto = ["bls/fake_crypto"]
diff --git a/eth2/state_processing/build.rs b/eth2/state_processing/build.rs
new file mode 120000
index 000000000..70d6c75b9
--- /dev/null
+++ b/eth2/state_processing/build.rs
@@ -0,0 +1 @@
+../utils/bls/build.rs
\ No newline at end of file
diff --git a/eth2/state_processing/tests/tests.rs b/eth2/state_processing/tests/tests.rs
index 03401b2c7..6ea8863b8 100644
--- a/eth2/state_processing/tests/tests.rs
+++ b/eth2/state_processing/tests/tests.rs
@@ -47,31 +47,28 @@ fn run_state_transition_test(test_name: &str) {
     // Run Tests
     let mut ok = true;
     for (i, test_case) in doc.test_cases.iter().enumerate() {
+        let fake_crypto = cfg!(feature = "fake_crypto");
+        if !test_case.verify_signatures == fake_crypto {
+            println!("Running {}", test_case.name);
+        } else {
+            println!(
+                "Skipping {} (fake_crypto: {}, need fake: {})",
+                test_case.name, fake_crypto, !test_case.verify_signatures
+            );
+            continue;
+        }
         let mut state = test_case.initial_state.clone();
         for (j, block) in test_case.blocks.iter().enumerate() {
             while block.slot > state.slot {
                 let latest_block_header = state.latest_block_header.clone();
                 per_slot_processing(&mut state, &latest_block_header, &test_case.config).unwrap();
             }
-            if test_case.verify_signatures {
-                let res = per_block_processing(&mut state, &block, &test_case.config);
-                if res.is_err() {
-                    println!("Error in {} (#{}), on block {}", test_case.name, i, j);
-                    println!("{:?}", res);
-                    ok = false;
-                };
-            } else {
-                let res = per_block_processing_without_verifying_block_signature(
-                    &mut state,
-                    &block,
-                    &test_case.config,
-                );
-                if res.is_err() {
-                    println!("Error in {} (#{}), on block {}", test_case.name, i, j);
-                    println!("{:?}", res);
-                    ok = false;
-                }
-            }
+            let res = per_block_processing(&mut state, &block, &test_case.config);
+            if res.is_err() {
+                println!("Error in {} (#{}), on block {}", test_case.name, i, j);
+                println!("{:?}", res);
+                ok = false;
+            };
         }
     }
 
diff --git a/eth2/utils/bls/Cargo.toml b/eth2/utils/bls/Cargo.toml
index 439debdcb..4ce499580 100644
--- a/eth2/utils/bls/Cargo.toml
+++ b/eth2/utils/bls/Cargo.toml
@@ -13,3 +13,6 @@ serde_derive = "1.0"
 serde_hex = { path = "../serde_hex" }
 ssz = { path = "../ssz" }
 tree_hash = { path = "../tree_hash" }
+
+[features]
+fake_crypto = []
diff --git a/eth2/utils/bls/build.rs b/eth2/utils/bls/build.rs
new file mode 100644
index 000000000..7f08a1ed5
--- /dev/null
+++ b/eth2/utils/bls/build.rs
@@ -0,0 +1,19 @@
+// This build script is symlinked from each project that requires BLS's "fake crypto",
+// so that the `fake_crypto` feature of every sub-crate can be turned on by running
+// with FAKE_CRYPTO=1 from the top-level workspace.
+// At some point in the future it might be possible to do:
+// $ cargo test --all --release --features fake_crypto
+// but at the present time this doesn't work.
+// Related: https://github.com/rust-lang/cargo/issues/5364
+fn main() {
+    if let Ok(fake_crypto) = std::env::var("FAKE_CRYPTO") {
+        if fake_crypto == "1" {
+            println!("cargo:rustc-cfg=feature=\"fake_crypto\"");
+            println!("cargo:rerun-if-env-changed=FAKE_CRYPTO");
+            println!(
+                "cargo:warning=[{}]: Compiled with fake BLS cryptography. DO NOT USE, TESTING ONLY",
+                std::env::var("CARGO_PKG_NAME").unwrap()
+            );
+        }
+    }
+}
diff --git a/eth2/utils/bls/src/lib.rs b/eth2/utils/bls/src/lib.rs
index b9a4d5c1d..fae41aeed 100644
--- a/eth2/utils/bls/src/lib.rs
+++ b/eth2/utils/bls/src/lib.rs
@@ -6,22 +6,22 @@ mod keypair;
 mod public_key;
 mod secret_key;
 
-#[cfg(not(debug_assertions))]
+#[cfg(not(feature = "fake_crypto"))]
 mod aggregate_signature;
-#[cfg(not(debug_assertions))]
+#[cfg(not(feature = "fake_crypto"))]
 mod signature;
-#[cfg(not(debug_assertions))]
+#[cfg(not(feature = "fake_crypto"))]
 pub use crate::aggregate_signature::AggregateSignature;
-#[cfg(not(debug_assertions))]
+#[cfg(not(feature = "fake_crypto"))]
 pub use crate::signature::Signature;
 
-#[cfg(debug_assertions)]
+#[cfg(feature = "fake_crypto")]
 mod fake_aggregate_signature;
-#[cfg(debug_assertions)]
+#[cfg(feature = "fake_crypto")]
 mod fake_signature;
-#[cfg(debug_assertions)]
+#[cfg(feature = "fake_crypto")]
 pub use crate::fake_aggregate_signature::FakeAggregateSignature as AggregateSignature;
-#[cfg(debug_assertions)]
+#[cfg(feature = "fake_crypto")]
 pub use crate::fake_signature::FakeSignature as Signature;
 
 pub use crate::aggregate_public_key::AggregatePublicKey;