diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 71b8a6e642..83ec786c5a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -101,13 +101,13 @@ test:osx:
   parallel:
     matrix:
       - jobname: osx-clang
-        image: macos-14-xcode-15
+        image: macos-15-xcode-16
         CC: clang
       - jobname: osx-reftable
-        image: macos-14-xcode-15
+        image: macos-15-xcode-16
         CC: clang
       - jobname: osx-meson
-        image: macos-14-xcode-15
+        image: macos-15-xcode-16
         CC: clang
   artifacts:
     paths:
diff --git a/meson.build b/meson.build
index 9e5f9d4c54..f7a6ccf6fb 100644
--- a/meson.build
+++ b/meson.build
@@ -1042,42 +1042,52 @@ if iconv.found()
     have_old_iconv = true
   endif
 
-  iconv_omits_bom_source = '''#
-    #include <iconv.h>
+  if meson.can_run_host_binaries()
+    if compiler.run('''
+      #include <iconv.h>
 
-    int main(int argc, const char **argv)
-    {
-  '''
-  if have_old_iconv
-    iconv_omits_bom_source += '''
-      typedef const char *iconv_ibp;
-    '''
-  else
-    iconv_omits_bom_source += '''
-      typedef char *iconv_ibp;
-    '''
-  endif
-  iconv_omits_bom_source += '''
-      int v;
-      iconv_t conv;
-      char in[] = "a"; iconv_ibp pin = in;
-      char out[20] = ""; char *pout = out;
-      size_t isz = sizeof in;
-      size_t osz = sizeof out;
+      int main(int argc, const char **argv)
+      {
+        char in[] = "a", *inpos = in;
+        char out[20] = "", *outpos = out;
+        size_t insz = sizeof(in), outsz = sizeof(out);
+        iconv_t conv = iconv_open("UTF-16", "UTF-8");
+        iconv(conv, (void *) &inpos, &insz, &outpos, &outsz);
+        iconv_close(conv);
+        return (unsigned char)(out[0]) + (unsigned char)(out[1]) != 0xfe + 0xff;
+      }
+    ''',
+      dependencies: iconv,
+      name: 'iconv omits BOM',
+    ).returncode() != 0
+      libgit_c_args += '-DICONV_OMITS_BOM'
+    endif
 
-      conv = iconv_open("UTF-16", "UTF-8");
-      iconv(conv, &pin, &isz, &pout, &osz);
-      iconv_close(conv);
-      v = (unsigned char)(out[0]) + (unsigned char)(out[1]);
-      return v != 0xfe + 0xff;
-    }
-  '''
+    if compiler.run('''
+      #include <iconv.h>
+      #include <string.h>
 
-  if meson.can_run_host_binaries() and compiler.run(iconv_omits_bom_source,
-    dependencies: iconv,
-    name: 'iconv omits BOM',
-  ).returncode() != 0
-    libgit_c_args += '-DICONV_OMITS_BOM'
+      int main(int argc, const char *argv[])
+      {
+          char in[] = "\x1b\x24\x42\x24\x22\x24\x22\x1b\x28\x42", *inpos = in;
+          char out[7] = { 0 }, *outpos = out;
+          size_t insz = sizeof(in) - 1, outsz = 4;
+          iconv_t conv = iconv_open("UTF-8", "ISO-2022-JP");
+          if (!conv)
+              return 1;
+          if (iconv(conv, (void *) &inpos, &insz, &outpos, &outsz) != (size_t) -1)
+              return 2;
+          outsz = sizeof(out) - (outpos - out);
+          if (iconv(conv, (void *) &inpos, &insz, &outpos, &outsz) == (size_t) -1)
+              return 3;
+          return strcmp("\343\201\202\343\201\202", out) ? 4 : 0;
+      }
+    ''',
+      dependencies: iconv,
+      name: 'iconv handles restarts properly',
+    ).returncode() != 0
+      libgit_c_args += '-DICONV_RESTART_RESET'
+    endif
   endif
 else
   libgit_c_args += '-DNO_ICONV'