diff --git a/pkgs/development/compilers/llvm/15/default.nix b/pkgs/development/compilers/llvm/15/default.nix
index 863d31874ec8..6a3b8cbabab7 100644
--- a/pkgs/development/compilers/llvm/15/default.nix
+++ b/pkgs/development/compilers/llvm/15/default.nix
@@ -266,11 +266,13 @@ in let
         targetLlvmLibraries.compiler-rt
       ];
       extraBuildCommands = mkExtraBuildCommands cc;
-      nixSupport.cc-cflags = [
-        "-rtlib=compiler-rt"
-        "-B${targetLlvmLibraries.compiler-rt}/lib"
-        "-nostdlib++"
-      ];
+      nixSupport.cc-cflags =
+        [
+          "-rtlib=compiler-rt"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+          "-nostdlib++"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
     };
 
     clangNoLibc = wrapCCWith rec {
@@ -281,10 +283,12 @@ in let
         targetLlvmLibraries.compiler-rt
       ];
       extraBuildCommands = mkExtraBuildCommands cc;
-      nixSupport.cc-cflags = [
-        "-rtlib=compiler-rt"
-        "-B${targetLlvmLibraries.compiler-rt}/lib"
-      ];
+      nixSupport.cc-cflags =
+        [
+          "-rtlib=compiler-rt"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
     };
 
     clangNoCompilerRt = wrapCCWith rec {
@@ -293,16 +297,22 @@ in let
       bintools = bintoolsNoLibc';
       extraPackages = [ ];
       extraBuildCommands = mkExtraBuildCommands0 cc;
-      nixSupport.cc-cflags = [ "-nostartfiles" ];
+      nixSupport.cc-cflags =
+        [
+          "-nostartfiles"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
     };
 
-    clangNoCompilerRtWithLibc = wrapCCWith rec {
+    clangNoCompilerRtWithLibc = wrapCCWith (rec {
       cc = tools.clang-unwrapped;
       libcxx = null;
       bintools = bintools';
       extraPackages = [ ];
       extraBuildCommands = mkExtraBuildCommands0 cc;
-    };
+    } // lib.optionalAttrs stdenv.targetPlatform.isWasm {
+      nixSupport.cc-cflags = [ "-fno-exceptions" ];
+    });
 
   });
 
diff --git a/pkgs/development/compilers/llvm/16/default.nix b/pkgs/development/compilers/llvm/16/default.nix
index a9ffac74123a..541db8c400de 100644
--- a/pkgs/development/compilers/llvm/16/default.nix
+++ b/pkgs/development/compilers/llvm/16/default.nix
@@ -271,11 +271,13 @@ in let
         targetLlvmLibraries.compiler-rt
       ];
       extraBuildCommands = mkExtraBuildCommands cc;
-      nixSupport.cc-cflags = [
-        "-rtlib=compiler-rt"
-        "-B${targetLlvmLibraries.compiler-rt}/lib"
-        "-nostdlib++"
-      ];
+      nixSupport.cc-cflags =
+        [
+          "-rtlib=compiler-rt"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+          "-nostdlib++"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
     };
 
     clangNoLibc = wrapCCWith rec {
@@ -286,10 +288,12 @@ in let
         targetLlvmLibraries.compiler-rt
       ];
       extraBuildCommands = mkExtraBuildCommands cc;
-      nixSupport.cc-cflags = [
-        "-rtlib=compiler-rt"
-        "-B${targetLlvmLibraries.compiler-rt}/lib"
-      ];
+      nixSupport.cc-cflags =
+        [
+          "-rtlib=compiler-rt"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
     };
 
     clangNoCompilerRt = wrapCCWith rec {
@@ -298,16 +302,22 @@ in let
       bintools = bintoolsNoLibc';
       extraPackages = [ ];
       extraBuildCommands = mkExtraBuildCommands0 cc;
-      nixSupport.cc-cflags = [ "-nostartfiles" ];
+      nixSupport.cc-cflags =
+        [
+          "-nostartfiles"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
     };
 
-    clangNoCompilerRtWithLibc = wrapCCWith rec {
+    clangNoCompilerRtWithLibc = wrapCCWith (rec {
       cc = tools.clang-unwrapped;
       libcxx = null;
       bintools = bintools';
       extraPackages = [ ];
       extraBuildCommands = mkExtraBuildCommands0 cc;
-    };
+    } // lib.optionalAttrs stdenv.targetPlatform.isWasm {
+      nixSupport.cc-cflags = [ "-fno-exceptions" ];
+    });
 
     # Has to be in tools despite mostly being a library,
     # because we use a native helper executable from a