diff --git a/pkgs/development/compilers/yosys/default.nix b/pkgs/development/compilers/yosys/default.nix
index 06ce12d642e3..6af75057e898 100644
--- a/pkgs/development/compilers/yosys/default.nix
+++ b/pkgs/development/compilers/yosys/default.nix
@@ -1,6 +1,5 @@
 { stdenv
 , lib
-, bash
 , bison
 , boost
 , fetchFromGitHub
@@ -76,13 +75,13 @@ let
 
 in stdenv.mkDerivation (finalAttrs: {
   pname   = "yosys";
-  version = "0.42";
+  version = "0.43";
 
   src = fetchFromGitHub {
     owner = "YosysHQ";
     repo  = "yosys";
     rev   = "refs/tags/${finalAttrs.pname}-${finalAttrs.version}";
-    hash  = "sha256-P0peg81wxCG0Bw2EJEX5WuDYU7GmRqgRw2SyWK/CGNI=";
+    hash  = "sha256-MJTtQvHsHvuo4aNNYSPxSMbeXCty66q83/sbp1Yiiv4=";
     fetchSubmodules = true;
     leaveDotGit = true;
     postFetch = ''
@@ -122,7 +121,6 @@ in stdenv.mkDerivation (finalAttrs: {
     substituteInPlace ./Makefile \
       --replace-fail 'echo UNKNOWN' 'echo ${builtins.substring 0 10 finalAttrs.src.rev}'
 
-    chmod +x ./misc/yosys-config.in
     patchShebangs tests ./misc/yosys-config.in
   '';
 
diff --git a/pkgs/development/compilers/yosys/fix-clang-build.patch b/pkgs/development/compilers/yosys/fix-clang-build.patch
index 7f93594d0c1d..05ba4fbc5929 100644
--- a/pkgs/development/compilers/yosys/fix-clang-build.patch
+++ b/pkgs/development/compilers/yosys/fix-clang-build.patch
@@ -9,6 +9,14 @@
      ./cxxrtl-test-${subtest}
  }
  
+@@ -14,4 +14,4 @@ run_subtest value_fuzz
+ 
+ # Compile-only test.
+ ../../yosys -p "read_verilog test_unconnected_output.v; proc; clean; write_cxxrtl cxxrtl-test-unconnected_output.cc"
+-${CC:-gcc} -std=c++11 -c -o cxxrtl-test-unconnected_output -I../../backends/cxxrtl/runtime cxxrtl-test-unconnected_output.cc
++${CXX:-gcc} -std=c++11 -c -o cxxrtl-test-unconnected_output -I../../backends/cxxrtl/runtime cxxrtl-test-unconnected_output.cc
+diff --git a/tests/fmt/run-test.sh b/tests/fmt/run-test.sh
+index 998047f83..2a4a59f01 100644
 --- a/tests/fmt/run-test.sh
 +++ b/tests/fmt/run-test.sh
 @@ -51,7 +51,7 @@ test_cxxrtl () {