diff --git a/contrib/nix/ruby2.4-shell.nix b/contrib/nix/ruby2.4-shell.nix
index e02a4293..27ce3af7 100644
--- a/contrib/nix/ruby2.4-shell.nix
+++ b/contrib/nix/ruby2.4-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
       # Workaround: remove rake from nativeBuildInputs, otherwise it causes
       # xapian-bindings to build against the default Ruby version
       # instead of our chosen version.
diff --git a/contrib/nix/ruby2.5-shell.nix b/contrib/nix/ruby2.5-shell.nix
index a37818e5..fdb42167 100644
--- a/contrib/nix/ruby2.5-shell.nix
+++ b/contrib/nix/ruby2.5-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
       # Workaround: remove rake from nativeBuildInputs, otherwise it causes
       # xapian-bindings to build against the default Ruby version
       # instead of our chosen version.
diff --git a/contrib/nix/ruby2.6-shell.nix b/contrib/nix/ruby2.6-shell.nix
index b3c69522..eefbd700 100644
--- a/contrib/nix/ruby2.6-shell.nix
+++ b/contrib/nix/ruby2.6-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
       # Workaround: remove rake from nativeBuildInputs, otherwise it causes
       # xapian-bindings to build against the default Ruby version
       # instead of our chosen version.
diff --git a/contrib/nix/ruby2.7-shell.nix b/contrib/nix/ruby2.7-shell.nix
index 20298b7d..0bfa30f5 100644
--- a/contrib/nix/ruby2.7-shell.nix
+++ b/contrib/nix/ruby2.7-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
     };
   };
 in pkgs.mkShell { packages = [ gems gems.wrappedRuby pkgs.pandoc ]; }
diff --git a/contrib/nix/ruby3.0-shell.nix b/contrib/nix/ruby3.0-shell.nix
index 4870cf67..76328c7e 100644
--- a/contrib/nix/ruby3.0-shell.nix
+++ b/contrib/nix/ruby3.0-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
     };
   };
 in pkgs.mkShell { packages = [ gems gems.wrappedRuby pkgs.pandoc ]; }
diff --git a/contrib/nix/ruby3.1-shell.nix b/contrib/nix/ruby3.1-shell.nix
index ee1a9f35..a50b079f 100644
--- a/contrib/nix/ruby3.1-shell.nix
+++ b/contrib/nix/ruby3.1-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
     };
   };
 in pkgs.mkShell { packages = [ gems gems.wrappedRuby pkgs.pandoc ]; }
diff --git a/contrib/nix/ruby3.2-shell.nix b/contrib/nix/ruby3.2-shell.nix
index 991b4554..ff7ec58c 100644
--- a/contrib/nix/ruby3.2-shell.nix
+++ b/contrib/nix/ruby3.2-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
     };
   };
 in pkgs.mkShell { packages = [ gems gems.wrappedRuby pkgs.pandoc ]; }
diff --git a/contrib/nix/ruby3.3-shell.nix b/contrib/nix/ruby3.3-shell.nix
index b4e40c61..7de9c440 100644
--- a/contrib/nix/ruby3.3-shell.nix
+++ b/contrib/nix/ruby3.3-shell.nix
@@ -24,6 +24,13 @@ let
           })
         ];
       };
+      # Workaround for a new error in clang 16 (MacOS):
+      # https://github.com/blackwinter/unicode/pull/11
+      unicode = attrs: {
+        buildFlags = [
+          "--with-cflags=-Wno-incompatible-function-pointer-types"
+        ];
+      };
     };
   };
 in pkgs.mkShell { packages = [ gems gems.wrappedRuby pkgs.pandoc ]; }