diff --git a/build.nims b/build.nims
index d694206d..6318e459 100644
--- a/build.nims
+++ b/build.nims
@@ -92,16 +92,6 @@ task testNatPcpMapping, "Run PCP NAT integration test (requires miniupnpd contai
   putEnv("STORAGE_INTEGRATION_TEST_INCLUDES", "nat/testnatpcp.nim")
   test "testIntegration", outName = "testIntegrationNatPcp"
 
-# Used to build the testing binaries in Docker
-task buildNatPortMappingBinaries, "Build UPnP and PCP NAT test binaries without running them":
-  buildBinary "storage",
-    outName = "storage",
-    params = "-d:chronicles_runtime_filtering -d:chronicles_log_level=TRACE"
-  putEnv("STORAGE_INTEGRATION_TEST_INCLUDES", "nat/testnatupnp.nim")
-  buildBinary "testIntegration", outName = "testIntegrationNat", srcDir = "tests/"
-  putEnv("STORAGE_INTEGRATION_TEST_INCLUDES", "nat/testnatpcp.nim")
-  buildBinary "testIntegration", outName = "testIntegrationNatPcp", srcDir = "tests/"
-
 task build, "build Logos Storage binary":
   storageTask()
 
diff --git a/tests/integration/nat/Dockerfile b/tests/integration/nat/Dockerfile
index 56c29ea9..1795e1e6 100644
--- a/tests/integration/nat/Dockerfile
+++ b/tests/integration/nat/Dockerfile
@@ -38,10 +38,9 @@ COPY library/ library/
 COPY tests/ tests/
 COPY build.nims config.nims storage.nim ./
 
-# Build libplum C library and Nim binaries.
-# ccache caches C compilation across builds; nimcache caches Nim's generated C files.
+# Build libplum C library. Nim binaries are compiled at test runtime.
+# ccache caches C compilation across builds.
 RUN --mount=type=cache,target=/root/.ccache \
-    --mount=type=cache,target=/app/nimcache \
     export PATH="/usr/lib/ccache:$PATH" && \
     rm -rf vendor/nim-libplum/vendor/libplum/build && \
     cmake -B vendor/nim-libplum/vendor/libplum/build \
@@ -49,9 +48,7 @@ RUN --mount=type=cache,target=/root/.ccache \
         vendor/nim-libplum/vendor/libplum && \
     make -j$(nproc) -C vendor/nim-libplum/vendor/libplum/build && \
     cp vendor/nim-libplum/vendor/libplum/build/libplum.a \
-        vendor/nim-libplum/vendor/libplum/libplum.a && \
-    USE_SYSTEM_NIM=1 vendor/nimbus-build-system/scripts/env.sh \
-    nim buildNatPortMappingBinaries -d:debug -d:disable_libbacktrace build.nims
+        vendor/nim-libplum/vendor/libplum/libplum.a
 
 COPY tests/integration/nat/docker-entrypoint.sh /entrypoint.sh
 RUN chmod +x /entrypoint.sh
diff --git a/tests/integration/nat/docker-entrypoint.sh b/tests/integration/nat/docker-entrypoint.sh
index 1d5b9df9..921a740e 100644
--- a/tests/integration/nat/docker-entrypoint.sh
+++ b/tests/integration/nat/docker-entrypoint.sh
@@ -45,17 +45,21 @@ EOF
   echo "miniupnpd started (pid $MINIUPNPD_PID)"
 }
 
+export DEBUG=${DEBUG:-0}
+
 if [[ "${TEST_PCP:-0}" == "1" ]]; then
   # PCP requires the UDP source IP to match the client_address in the MAP request.
   # Point the default route at LAN_IP so libplum uses it as both gateway and PCP target.
   ip route replace default via "$LAN_IP" dev "$LAN_IF"
   start_miniupnpd yes
   failed=0
-  DEBUG=${DEBUG:-0} /app/build/testIntegrationNatPcp || failed=1
+  USE_SYSTEM_NIM=1 vendor/nimbus-build-system/scripts/env.sh \
+    nim testNatPcpMapping -d:debug -d:disable_libbacktrace build.nims || failed=1
 else
   start_miniupnpd no
   failed=0
-  DEBUG=${DEBUG:-0} /app/build/testIntegrationNat || failed=1
+  USE_SYSTEM_NIM=1 vendor/nimbus-build-system/scripts/env.sh \
+    nim testNatPortMapping -d:debug -d:disable_libbacktrace build.nims || failed=1
 fi
 
 if [[ "${DEBUG:-0}" == "1" ]]; then