diff --git a/zero-gravity/zerog.Dockerfile b/zero-gravity/zerog.Dockerfile
index 152a9016..7c2b1422 100644
--- a/zero-gravity/zerog.Dockerfile
+++ b/zero-gravity/zerog.Dockerfile
@@ -8,11 +8,46 @@ RUN chmod +x /usr/local/bin/init.sh
 
 ARG ZERO_GRAVITY_VERSION
 ARG ZERO_GRAVITY_CHAIN_SPEC
-RUN if [ "${ZERO_GRAVITY_CHAIN_SPEC}" = "aristotle" ]; then \
-        curl -sL https://github.com/0gfoundation/0gchain-Aristotle/releases/download/${ZERO_GRAVITY_VERSION}/${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}.tar.gz -o /tmp/${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}.tar.gz; \
+
+# 0G publishes each network from a DIFFERENT repository, and the release-tag format is not
+# consistent within either of them. The asset filename is always "<spec>-v<version>.tar.gz";
+# only the tag varies:
+#
+#   aristotle -> 0gchain-Aristotle   1.0.4 = "1.0.4"      1.0.6 = "v1.0.6"
+#   galileo   -> 0gchain-NG          3.0.3 = "v3.0.3"     3.0.7 = "galileo-v3.0.7"   3.0.8 = "v3.0.8"
+#
+# So the tag cannot be hardcoded. Resolve it by trying the known forms in order and taking
+# the first that actually yields the asset.
+#
+# curl uses -f (fail on HTTP error). Without it a 404 HTML body is written into the .tar.gz
+# and the build dies several layers later at "tar: not in gzip format" -- an error that
+# points nowhere near the real cause. That has cost three separate misdiagnoses.
+RUN set -eu; \
+    ASSET="${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}.tar.gz"; \
+    if [ "${ZERO_GRAVITY_CHAIN_SPEC}" = "aristotle" ]; then \
+        REPO="0gfoundation/0gchain-Aristotle"; \
+        TAGS="${ZERO_GRAVITY_VERSION} v${ZERO_GRAVITY_VERSION} ${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}"; \
     else \
-        curl -sL https://github.com/0gfoundation/0gchain-NG/releases/download/v${ZERO_GRAVITY_VERSION}/${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}.tar.gz -o /tmp/${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}.tar.gz; \
+        REPO="0gfoundation/0gchain-NG"; \
+        TAGS="v${ZERO_GRAVITY_VERSION} ${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION} ${ZERO_GRAVITY_VERSION}"; \
+    fi; \
+    for TAG in ${TAGS}; do \
+        URL="https://github.com/${REPO}/releases/download/${TAG}/${ASSET}"; \
+        echo "0g: trying tag '${TAG}' -> ${URL}"; \
+        if curl -fsSL "${URL}" -o "/tmp/${ASSET}"; then \
+            echo "0g: resolved ${ZERO_GRAVITY_CHAIN_SPEC} ${ZERO_GRAVITY_VERSION} from tag '${TAG}'"; \
+            break; \
+        fi; \
+        rm -f "/tmp/${ASSET}"; \
+    done; \
+    if [ ! -s "/tmp/${ASSET}" ]; then \
+        echo "0g: FATAL - no release asset '${ASSET}' found in ${REPO} under any of: ${TAGS}" >&2; \
+        echo "0g: aristotle and galileo are SEPARATE repos on SEPARATE version lines" >&2; \
+        echo "0g: aristotle = 0gchain-Aristotle (1.0.x), galileo = 0gchain-NG (3.0.x)" >&2; \
+        echo "0g: check that version '${ZERO_GRAVITY_VERSION}' exists for '${ZERO_GRAVITY_CHAIN_SPEC}'" >&2; \
+        exit 1; \
     fi
+
 RUN tar -xzf /tmp/${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}.tar.gz -C /tmp
 RUN if [ "${ZERO_GRAVITY_CHAIN_SPEC}" = "galileo" ]; then \
         mv /tmp/${ZERO_GRAVITY_CHAIN_SPEC}-v${ZERO_GRAVITY_VERSION}/rpc /0g; \
@@ -26,4 +61,4 @@ RUN if [ "${ZERO_GRAVITY_CHAIN_SPEC}" = "galileo" ]; then \
 RUN chmod +x /0g/bin/0gchaind
 RUN chmod +x /0g/bin/geth
 
-ENTRYPOINT [ "init.sh" ]
\ No newline at end of file
+ENTRYPOINT [ "init.sh" ]