diff --git a/src/core-init-ext.nix b/src/core-init-ext.nix
index 3112d63..32738c1 100644
--- a/src/core-init-ext.nix
+++ b/src/core-init-ext.nix
@@ -67,9 +67,32 @@ in stdenv.mkDerivation (finalAttrs: {
     runHook postInstall
   '';
 
-  # TODO: Add a checkphase that runs nm on the provided extensions to ensure the expected symbols are present.
-  #       Also verify that the `sqlite_api` symbol is not present, and give a nice warning about using -DSQLITE_CORE
-  #       if it is.
+  doCheck = true;
+  checkPhase = ''
+    runHook preCheck
+
+    for ext in ${lib.escapeShellArgs (builtins.catAttrs "library" extensions)}; do
+      if nm -g --defined-only "$ext" | grep -q " sqlite_api$"; then
+        echo "Extension $ext appears to reference the 'sqlite_api' symbol, which is not expected for extensions which are going to be statically linked."
+        echo "If your are building the extension yourself, please ensure that it is built with \`-DSQLITE_CORE\`"
+        exit 1
+      fi
+    done
+
+    declare -A expectedSymbols;
+    ${lib.concatMapStringsSep "\n" (ext: "expectedSymbols[${lib.escapeShellArg ext.init}]=${lib.escapeShellArg ext.library};") extensions}
+    ${lib.concatMapStringsSep "\n" (ext: "expectedSymbols[${lib.escapeShellArg ext.shutdown}]=${lib.escapeShellArg ext.library};") (lib.filter (ext: ext.shutdown or null != null) extensions)}
+
+    for sym in "''${!expectedSymbols[@]}"; do
+      if ! nm -g --defined-only "''${expectedSymbols[$sym]}" | grep -q " ''${sym}$"; then
+        echo "Expected symbol $sym not found in ''${expectedSymbols[$sym]}."
+        exit 1
+      fi
+    done
+
+    runHook postCheck
+  '';
+
 
   passthru = {
     extraLDFLAGS = [