diff --git a/constructor/header.sh b/constructor/header.sh
index 0a5d740f..ec3b03d6 100644
--- a/constructor/header.sh
+++ b/constructor/header.sh
@@ -35,27 +35,29 @@ fi
 {%- elif linux and min_glibc_version %}
 min_glibc_version="{{ min_glibc_version }}"
 system_glibc_version="${CONDA_OVERRIDE_GLIBC:-}"
-case "$(ldd --version 2>&1)" in
-    *musl*)
-        # musl ldd will report musl version; call libc.so directly
-        # see https://github.com/conda/constructor/issues/850#issuecomment-2343756454
-        libc_so="$(find /lib /usr/local/lib /usr/lib -name 'libc.so.*' -print -quit 2>/dev/null)"
-        if [ -z "${libc_so}" ]; then
-            libc_so="$(strings /etc/ld.so.cache | grep '^/.*/libc\.so.*' | head -1)"
-        fi
-        if [ -z "${libc_so}" ]; then
-            echo "Warning: Couldn't find libc.so; won't be able to determine GLIBC version!" >&2
-            echo "Override by setting CONDA_OVERRIDE_GLIBC" >&2
-            system_glibc_version="0.0"
-        else
-            system_glibc_version=$("${libc_so}" --version | awk 'NR==1{ sub(/\.$/, ""); print $NF}')
-        fi
-    ;;
-    *)
-        # ldd reports glibc in the last field of the first line
-        system_glibc_version=$(ldd --version | awk 'NR==1{print $NF}')
-    ;;
-esac
+if [ "${system_glibc_version}" = "" ]; then
+    case "$(ldd --version 2>&1)" in
+        *musl*)
+            # musl ldd will report musl version; call libc.so directly
+            # see https://github.com/conda/constructor/issues/850#issuecomment-2343756454
+            libc_so="$(find /lib /usr/local/lib /usr/lib -name 'libc.so.*' -print -quit 2>/dev/null)"
+            if [ -z "${libc_so}" ]; then
+                libc_so="$(strings /etc/ld.so.cache | grep '^/.*/libc\.so.*' | head -1)"
+            fi
+            if [ -z "${libc_so}" ]; then
+                echo "Warning: Couldn't find libc.so; won't be able to determine GLIBC version!" >&2
+                echo "Override by setting CONDA_OVERRIDE_GLIBC" >&2
+                system_glibc_version="0.0"
+            else
+                system_glibc_version=$("${libc_so}" --version | awk 'NR==1{ sub(/\.$/, ""); print $NF}')
+            fi
+        ;;
+        *)
+            # ldd reports glibc in the last field of the first line
+            system_glibc_version=$(ldd --version | awk 'NR==1{print $NF}')
+        ;;
+    esac
+fi
 # shellcheck disable=SC2183 disable=SC2046
 int_min_glibc_version="$(printf "%02d%02d%02d" $(echo "$min_glibc_version" | sed 's/\./ /g'))"
 # shellcheck disable=SC2183 disable=SC2046