diff --git a/.cppcheck.suppressions b/.cppcheck.suppressions
index 529324b48..154eebed2 100644
--- a/.cppcheck.suppressions
+++ b/.cppcheck.suppressions
@@ -3,3 +3,8 @@
 // because all the places we do this are valid and won't cause problems even
 // on a ILP64 platform because we're careful about using NULL rather than 0.
 varFuncNullUB
+// Suppress the warning about unmatched suppressions. At the moment these
+// warnings are emitted even when removing the suppression comment results in
+// the warning being suppressed. In other words this unmatchedSuppression
+// warnings are false positives.
+unmatchedSuppression
diff --git a/build_tools/lint.fish b/build_tools/lint.fish
index 6d69ff566..0b14e564a 100755
--- a/build_tools/lint.fish
+++ b/build_tools/lint.fish
@@ -114,7 +114,9 @@ if set -q c_files[1]
 
         echo
         echo ========================================
-        echo "Running `cppcheck --check-config` to identify missing includes similar problems"
+        echo 'Running `cppcheck --check-config` to identify missing includes similar problems.'
+        echo 'Ignore unmatchedSuppression warnings as they are probably false positives we'
+        echo 'cannot suppress.'
         echo ========================================
         cppcheck $cppcheck_args --check-config $c_files 2>&1
     end
diff --git a/src/autoload.cpp b/src/autoload.cpp
index a10de1364..dbfa54e9f 100644
--- a/src/autoload.cpp
+++ b/src/autoload.cpp
@@ -1,7 +1,6 @@
 // The classes responsible for autoloading functions and completions.
 #include "config.h"  // IWYU pragma: keep
 
-#include <assert.h>
 #include <errno.h>
 #include <pthread.h>
 #include <stddef.h>
diff --git a/src/builtin.cpp b/src/builtin.cpp
index 43b1b049d..2d099db15 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -28,7 +28,6 @@
 #include <time.h>
 #include <unistd.h>
 #include <wchar.h>
-#include <wctype.h>
 #include <algorithm>
 #include <map>
 #include <memory>
diff --git a/src/builtin_printf.cpp b/src/builtin_printf.cpp
index 645dd982b..d690dcc4d 100644
--- a/src/builtin_printf.cpp
+++ b/src/builtin_printf.cpp
@@ -54,7 +54,7 @@
 #include <limits.h>
 #include <locale.h>
 #include <stdarg.h>
-#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <wchar.h>
diff --git a/src/builtin_set.cpp b/src/builtin_set.cpp
index a210cbb75..71592d971 100644
--- a/src/builtin_set.cpp
+++ b/src/builtin_set.cpp
@@ -3,7 +3,9 @@
 
 #include <errno.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
+#include <unistd.h>
 #include <wchar.h>
 #include <wctype.h>
 #include <algorithm>
diff --git a/src/builtin_string.cpp b/src/builtin_string.cpp
index b19ad38e8..afa11ee4d 100644
--- a/src/builtin_string.cpp
+++ b/src/builtin_string.cpp
@@ -720,8 +720,8 @@ bool regex_replacer_t::replace_matches(const wchar_t *arg) {
             done = true;
         } else {
             bufsize = outlen;
-            // cppcheck-suppress memleakOnRealloc
-            output = (wchar_t *)realloc(output, sizeof(wchar_t) * bufsize);
+            wchar_t *new_output = (wchar_t *)realloc(output, sizeof(wchar_t) * bufsize);
+            if (new_output) output = new_output;
         }
     }
 
diff --git a/src/env.cpp b/src/env.cpp
index 0fcee01c5..d95e7e0cc 100644
--- a/src/env.cpp
+++ b/src/env.cpp
@@ -8,9 +8,7 @@
 #include <pwd.h>
 #include <stddef.h>
 #include <stdlib.h>
-#ifdef HAVE__NL_MSG_CAT_CNTR
 #include <string.h>
-#endif
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <time.h>
diff --git a/src/env_universal_common.cpp b/src/env_universal_common.cpp
index d0fcdab3c..c19222e63 100644
--- a/src/env_universal_common.cpp
+++ b/src/env_universal_common.cpp
@@ -17,7 +17,6 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <wchar.h>
-#include <wctype.h>
 #include <string>
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
diff --git a/src/exec.cpp b/src/exec.cpp
index bd6ae4560..b98a1d23f 100644
--- a/src/exec.cpp
+++ b/src/exec.cpp
@@ -9,7 +9,6 @@
 #include <fcntl.h>
 #include <signal.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <wchar.h>
diff --git a/src/fish.cpp b/src/fish.cpp
index cc84686c0..6f9dd50f5 100644
--- a/src/fish.cpp
+++ b/src/fish.cpp
@@ -17,7 +17,6 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */
 #include "config.h"
 
-#include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
@@ -47,13 +46,11 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 #include "function.h"
 #include "history.h"
 #include "input.h"
-#include "input_common.h"
 #include "io.h"
 #include "parser.h"
 #include "path.h"
 #include "proc.h"
 #include "reader.h"
-#include "wildcard.h"
 #include "wutil.h"  // IWYU pragma: keep
 
 // PATH_MAX may not exist.
diff --git a/src/history.cpp b/src/history.cpp
index 0f07f566f..9b2d0dd85 100644
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -1450,7 +1450,11 @@ static bool format_history_record(const history_item_t &item, const wchar_t *sho
         streams.out.append(timestamp_string);
     }
     streams.out.append(item.str());
-    streams.out.append(null_terminate ? L'\0' : L'\n');
+    if (null_terminate) {
+        streams.out.append(L'\0');
+    } else {
+        streams.out.append(L'\n');
+    }
     return true;
 }
 
diff --git a/src/history.h b/src/history.h
index a8aa51575..c6f55a679 100644
--- a/src/history.h
+++ b/src/history.h
@@ -7,6 +7,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <time.h>
+#include <wctype.h>
 #include <deque>
 #include <memory>
 #include <set>
diff --git a/src/pager.cpp b/src/pager.cpp
index 4a952c205..3c4adc7dd 100644
--- a/src/pager.cpp
+++ b/src/pager.cpp
@@ -3,7 +3,6 @@
 // IWYU pragma: no_include <cstddef>
 #include <assert.h>
 #include <stddef.h>
-#include <stdlib.h>
 #include <wchar.h>
 #include <wctype.h>
 #include <map>
diff --git a/src/parser.cpp b/src/parser.cpp
index 914fcf036..fa9bbe1d4 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -3,7 +3,6 @@
 
 #include <assert.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <wchar.h>
 #include <algorithm>
 #include <memory>
diff --git a/src/screen.cpp b/src/screen.cpp
index 54a1203f3..4fc38d691 100644
--- a/src/screen.cpp
+++ b/src/screen.cpp
@@ -31,7 +31,6 @@
 #include <vector>
 
 #include "common.h"
-#include "env.h"
 #include "fallback.h"  // IWYU pragma: keep
 #include "highlight.h"
 #include "output.h"
diff --git a/src/signal.cpp b/src/signal.cpp
index a718d250e..46e501b81 100644
--- a/src/signal.cpp
+++ b/src/signal.cpp
@@ -14,7 +14,6 @@
 #include "fallback.h"  // IWYU pragma: keep
 #include "proc.h"
 #include "reader.h"
-#include "signal.h"
 #include "wutil.h"  // IWYU pragma: keep
 
 /// Struct describing an entry for the lookup table used to convert between signal names and signal
diff --git a/src/tokenizer.cpp b/src/tokenizer.cpp
index 29d11639c..672c26693 100644
--- a/src/tokenizer.cpp
+++ b/src/tokenizer.cpp
@@ -5,7 +5,6 @@
 #include <assert.h>
 #include <fcntl.h>
 #include <limits.h>
-#include <stdlib.h>
 #include <unistd.h>
 #include <wchar.h>
 #include <wctype.h>
diff --git a/src/wutil.cpp b/src/wutil.cpp
index 25556c92f..48a37590c 100644
--- a/src/wutil.cpp
+++ b/src/wutil.cpp
@@ -16,6 +16,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <wchar.h>
+#include <wctype.h>
 #include <map>
 #include <memory>
 #include <string>
diff --git a/src/wutil.h b/src/wutil.h
index 601fac936..6037ef06d 100644
--- a/src/wutil.h
+++ b/src/wutil.h
@@ -3,6 +3,7 @@
 #define FISH_WUTIL_H
 
 #include <dirent.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <time.h>