diff --git a/src/jitter.rs b/src/jitter.rs
index 0e5b1bd0981..aeb9fd5d800 100644
--- a/src/jitter.rs
+++ b/src/jitter.rs
@@ -171,11 +171,11 @@ impl JitterRng {
 
         ec
     }
-    
+
     /// Configures how many rounds are used to generate each 64-bit value.
     /// This must be greater than zero, and has a big impact on performance
     /// and output quality.
-    /// 
+    ///
     /// `new_with_timer` conservatively uses 64 rounds, but often less rounds
     /// can be used. The `test_timer()` function returns the minimum number of
     /// rounds required for full strength (platform dependent), so one may use
@@ -437,6 +437,9 @@ impl JitterRng {
         // or check for `CONFIG_X86_TSC`, but it does not make much sense as the
         // following sanity checks verify that we have a high-resolution timer.
 
+        #[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
+        return Err(TimerError::NoTimer);
+
         let mut delta_sum = 0;
         let mut old_delta = 0;
 
@@ -549,7 +552,7 @@ impl JitterRng {
 
         const FACTOR: u32  = 3;
         fn log2(x: u64) -> u32 { 64 - x.leading_zeros() }
-        
+
         // pow(δ, FACTOR) must be representable; if you have overflow reduce FACTOR
         Ok(64 * 2 * FACTOR / (log2(delta_average.pow(FACTOR)) + 1))
     }
@@ -654,7 +657,7 @@ impl JitterRng {
     }
 }
 
-#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "windows")))]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "windows", all(target_arch = "wasm32", not(target_os = "emscripten")))))]
 fn get_nstime() -> u64 {
     use std::time::{SystemTime, UNIX_EPOCH};
 
@@ -693,6 +696,11 @@ fn get_nstime() -> u64 {
     t as u64
 }
 
+#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
+fn get_nstime() -> u64 {
+    unreachable!()
+}
+
 // A function that is opaque to the optimizer to assist in avoiding dead-code
 // elimination. Taken from `bencher`.
 fn black_box<T>(dummy: T) -> T {
diff --git a/src/os.rs b/src/os.rs
index a54e4eaa323..7ff61a738a5 100644
--- a/src/os.rs
+++ b/src/os.rs
@@ -544,6 +544,26 @@ mod imp {
     }
 }
 
+#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
+mod imp {
+    use std::io;
+    use Rng;
+
+    #[derive(Debug)]
+    pub struct OsRng;
+
+    impl OsRng {
+        pub fn new() -> io::Result<OsRng> {
+            Err(io::Error::new(io::ErrorKind::Other, "Not supported"))
+        }
+    }
+
+    impl Rng for OsRng {
+        fn next_u32(&mut self) -> u32 {
+            panic!("Not supported")
+        }
+    }
+}
 
 #[cfg(test)]
 mod test {