diff --git a/lib/emscripten/Cargo.toml b/lib/emscripten/Cargo.toml
index cfffe82f8..306512dac 100644
--- a/lib/emscripten/Cargo.toml
+++ b/lib/emscripten/Cargo.toml
@@ -21,7 +21,7 @@ rand = "0.6"
 [dev-dependencies]
 wasmer-clif-backend = { path = "../clif-backend", version = "0.2.0" }
 wabt = "0.7.2"
-wasmer-dynasm-backend = { path = "../dynasm-backend", version = "0.1.0" }
+wasmer-dynasm-backend = { path = "../dynasm-backend", version = "0.1.0", optional = true }
 
 [target.'cfg(not(windows))'.dev-dependencies]
 wasmer-llvm-backend = { path = "../llvm-backend", version = "0.1.0" }
@@ -32,4 +32,4 @@ glob = "0.2.11"
 [features]
 clif = []
 llvm = []
-dynasm = []
\ No newline at end of file
+dynasm = ["wasmer-dynasm-backend"]
\ No newline at end of file
diff --git a/lib/spectests/Cargo.toml b/lib/spectests/Cargo.toml
index 3318589f7..c83dd5ad6 100644
--- a/lib/spectests/Cargo.toml
+++ b/lib/spectests/Cargo.toml
@@ -16,7 +16,7 @@ wabt = "0.7.2"
 
 [dev-dependencies]
 wasmer-clif-backend = { path = "../clif-backend", version = "0.2.0" }
-wasmer-dynasm-backend = { path = "../dynasm-backend", version = "0.1.0" }
+wasmer-dynasm-backend = { path = "../dynasm-backend", version = "0.1.0", optional = true }
 wabt = "0.7.2"
 
 [target.'cfg(not(windows))'.dependencies]
@@ -27,4 +27,4 @@ default = ["fast-tests"]
 fast-tests = []
 clif = []
 llvm = ["wasmer-llvm-backend"]
-dynasm = []
\ No newline at end of file
+dynasm = ["wasmer-dynasm-backend"]
\ No newline at end of file