diff --git a/app/src/main/jni/Android.mk b/app/src/main/jni/Android.mk
index d0af3f0..8bd1a6d 100755
--- a/app/src/main/jni/Android.mk
+++ b/app/src/main/jni/Android.mk
@@ -78,20 +78,7 @@ LOCAL_SRC_FILES := httrack/src/htscore.c httrack/src/htsparse.c 			\
 	httrack/src/htsconcat.c httrack/src/htsmodules.c 						\
 	httrack/src/htscharset.c httrack/src/punycode.c 						\
 	httrack/src/htsencoding.c httrack/src/md5.c								\
-	httrack/src/htssniff.c httrack/src/htsselftest.c						\
-	httrack/src/htsselftest_util.c					\
-	httrack/src/htsback_selftest.c httrack/src/htscache_selftest.c	\
-	httrack/src/htsbundle_selftest.c					\
-	httrack/src/htscharset_selftest.c httrack/src/htscmdline_selftest.c	\
-	httrack/src/htscookie_selftest.c	\
-	httrack/src/htsdns_selftest.c httrack/src/htsfilters_selftest.c	\
-	httrack/src/htsheader_selftest.c httrack/src/htsio_selftest.c	\
-	httrack/src/htslib_selftest.c httrack/src/htslines_selftest.c	\
-	httrack/src/htsmime_selftest.c	\
-	httrack/src/htsname_selftest.c httrack/src/htsnet_selftest.c	\
-	httrack/src/htsopt_selftest.c httrack/src/htsparse_selftest.c	\
-	httrack/src/htstools_selftest.c	\
-	httrack/src/htswarc_selftest.c httrack/src/htswizard_selftest.c	\
+	httrack/src/htssniff.c						\
 	httrack/src/htscodec.c httrack/src/htsproxy.c							\
 	httrack/src/htsdate.c httrack/src/htsurlport.c httrack/src/htswarc.c							\
 	httrack/src/htsescape.c										\
@@ -99,9 +86,8 @@ LOCAL_SRC_FILES := httrack/src/htscore.c httrack/src/htsparse.c 			\
 	httrack/src/htssitemap.c httrack/src/htssinglefile.c					\
 	httrack/src/htschanges.c httrack/src/htscmdline.c						\
 	httrack/src/htslines.c													\
-	httrack/src/htsfetch.c httrack/src/htsfetch_selftest.c			\
+	httrack/src/htsfetch.c						\
 	httrack/src/htspsl.c httrack/src/htspsl_data.c					\
-	httrack/src/htspsl_selftest.c									\
 	httrack/src/htscrashtest.c												\
 	httrack/src/minizip/ioapi.c												\
 	httrack/src/minizip/mztools.c httrack/src/minizip/unzip.c				\
@@ -127,6 +113,9 @@ LOCAL_CFLAGS += -O3 -g3 -funwind-tables -fPIC 					\
 	-Wno-nested-externs														\
 	-D_REENTRANT -DPIC -DANDROID -D_ANDROID -DHAVE_CONFIG_H -DINET6 -DHTS_INTERNAL_BUILD			\
 	-DLIBHTTRACK_EXPORTS -DZLIB_CONST -DHTS_INTHASH_USES_MD5 -DLIBICONV_PLUG
+# The app never asks the engine for a self-test. The sources are gone from
+# LOCAL_SRC_FILES above too, because htsselftest_int.h #errors under this macro.
+LOCAL_CFLAGS += -DHTS_NO_SELFTEST
 LOCAL_CPPFLAGS += -pthread
 include $(BUILD_SHARED_LIBRARY)
 
diff --git a/app/src/test/java/com/httrack/android/CodeqlScopeTest.java b/app/src/test/java/com/httrack/android/CodeqlScopeTest.java
index 63f4772..a54b251 100644
--- a/app/src/test/java/com/httrack/android/CodeqlScopeTest.java
+++ b/app/src/test/java/com/httrack/android/CodeqlScopeTest.java
@@ -19,7 +19,6 @@
  */
 public class CodeqlScopeTest {
   private static final String WORKFLOW = ".github/workflows/codeql.yml";
-  private static final String ANDROID_MK = "app/src/main/jni/Android.mk";
   private static final String UNTRACED = "Build the engine, untraced";
   private static final String TRACED = "Recompile the JNI glue, traced";
   private static final String INIT = "github/codeql-action/init";
@@ -37,7 +36,7 @@ private static String flattened(final String path) throws IOException {
 
   /** Every source the htslibjni module builds, "+=" included, so an appended one is not missed. */
   private static Set<String> glueSources() throws IOException {
-    final String mk = flattened(ANDROID_MK);
+    final String mk = TestSources.flattenedMakefile();
     final Matcher module = Pattern.compile("LOCAL_MODULE\\s*:=\\s*htslibjni\\b").matcher(mk);
     assertTrue("Android.mk must still define the htslibjni module", module.find());
     final String body = mk.substring(module.end()).split("include \\$\\(BUILD")[0];
diff --git a/app/src/test/java/com/httrack/android/EngineSelftestsExcludedTest.java b/app/src/test/java/com/httrack/android/EngineSelftestsExcludedTest.java
new file mode 100644
index 0000000..a50d526
--- /dev/null
+++ b/app/src/test/java/com/httrack/android/EngineSelftestsExcludedTest.java
@@ -0,0 +1,64 @@
+package com.httrack.android;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.LinkedHashSet;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.junit.Test;
+
+/**
+ * The engine refuses to compile a self-test source under HTS_NO_SELFTEST, so re-adding one to
+ * Android.mk breaks the build. A later engine could add a self-test that does not include that
+ * header, and then nothing would notice, so hold the engine's own list against ours.
+ */
+public class EngineSelftestsExcludedTest {
+  /** The sources the engine builds only when self-tests are wanted, basenames. */
+  private static Set<String> engineSelftests() throws IOException {
+    final String makefile = TestSources.read(TestSources.engineFile("src/Makefile.am"))
+        .replaceAll("\\\\\n\\s*", " ");
+    final String block = TestSources.between(makefile, "if SELFTESTS", "endif");
+    final Matcher sources = Pattern.compile("_SOURCES\\s*[:+]?=\\s*([^\n]*)").matcher(block);
+    final Set<String> all = new LinkedHashSet<String>();
+    assertTrue("the engine must still gate its self-tests on SELFTESTS", sources.find());
+    do {
+      all.addAll(Arrays.asList(sources.group(1).trim().split("\\s+")));
+    } while (sources.find());
+    return all;
+  }
+
+  /** Basenames of the engine sources the libhttrack module builds. */
+  private static Set<String> engineSourcesBuilt() throws IOException {
+    final String mk = TestSources.flattenedMakefile();
+    final Matcher module = Pattern.compile("LOCAL_MODULE\\s*:=\\s*libhttrack\\b").matcher(mk);
+    assertTrue("Android.mk must still define the libhttrack module", module.find());
+    final String body = mk.substring(module.end()).split("include \\$\\(BUILD")[0];
+    final Matcher sources = Pattern.compile("LOCAL_SRC_FILES\\s*[:+]?=\\s*([^\n]*)").matcher(body);
+    final Set<String> all = new LinkedHashSet<String>();
+    assertTrue("the libhttrack module must still carry a source list", sources.find());
+    do {
+      for (final String path : sources.group(1).trim().split("\\s+")) {
+        all.add(path.substring(path.lastIndexOf('/') + 1));
+      }
+    } while (sources.find());
+    return all;
+  }
+
+  @Test
+  public void noEngineSelftestIsBuilt() throws IOException {
+    final Set<String> selftests = engineSelftests();
+    final Set<String> built = engineSourcesBuilt();
+    assertFalse("no self-test source parsed, so this test would pass on anything",
+        selftests.isEmpty());
+    // Control: an engine source that must be built, or the list above could be read as empty.
+    assertTrue("htscore.c must still be built", built.contains("htscore.c"));
+    final Set<String> both = new LinkedHashSet<String>(built);
+    both.retainAll(selftests);
+    assertTrue("the APK must not build the engine self-tests: " + both, both.isEmpty());
+  }
+}
diff --git a/app/src/test/java/com/httrack/android/TestSources.java b/app/src/test/java/com/httrack/android/TestSources.java
index 3763635..d1dd14d 100644
--- a/app/src/test/java/com/httrack/android/TestSources.java
+++ b/app/src/test/java/com/httrack/android/TestSources.java
@@ -57,6 +57,12 @@ static File resFile(final String name) {
     return new File(dir("src/main/res"), name);
   }
 
+  /** Android.mk, free of CRLF and line continuations, so a wrapped list matches in one line. */
+  static String flattenedMakefile() throws IOException {
+    return read(new File(dir("src/main/jni"), "Android.mk")).replace("\r", "")
+        .replaceAll("\\\\\n\\s*", " ");
+  }
+
   static String read(final File file) throws IOException {
     return new String(Files.readAllBytes(file.toPath()), "UTF-8");
   }