diff --git a/nvm.sh b/nvm.sh
index d771dbe4..382e174c 100755
--- a/nvm.sh
+++ b/nvm.sh
@@ -1015,6 +1015,27 @@ nvm_is_valid_version() {
     *)
       local VERSION
       VERSION="$(nvm_strip_iojs_prefix "${1-}")"
+      local NVM_VERSION_CORE
+      NVM_VERSION_CORE="${VERSION#v}"
+      case "${NVM_VERSION_CORE}" in
+        *-*)
+          # prereleases (rc, nightly, v8-canary, ...) need a full x.y.z, and never have a dot followed by a non-digit, like a file extension
+          case "${NVM_VERSION_CORE#*-}" in
+            '' | .* | *. | *..* | *.*[!0-9.]* | *[!0-9A-Za-z.-]*) return 1 ;;
+          esac
+          NVM_VERSION_CORE="${NVM_VERSION_CORE%%-*}"
+          case "${NVM_VERSION_CORE}" in
+            *.*.*) ;;
+            *) return 1 ;;
+          esac
+        ;;
+        *.)
+          NVM_VERSION_CORE="${NVM_VERSION_CORE%.}"
+        ;;
+      esac
+      case "${NVM_VERSION_CORE}" in
+        '' | .* | *. | *..* | *.*.*.* | *[!0-9.]*) return 1 ;;
+      esac
       nvm_version_greater_than_or_equal_to "${VERSION}" 0
     ;;
   esac
diff --git a/test/fast/Running 'nvm exec' and 'nvm run' treat digit-named files as arguments, not versions b/test/fast/Running 'nvm exec' and 'nvm run' treat digit-named files as arguments, not versions
new file mode 100755
index 00000000..756752d7
--- /dev/null
+++ b/test/fast/Running 'nvm exec' and 'nvm run' treat digit-named files as arguments, not versions	
@@ -0,0 +1,66 @@
+#!/bin/sh
+
+set -ex
+
+die () { echo "$@" ; cleanup ; exit 1; }
+
+cleanup() {
+  cd "${ORIG_PWD}" 2>/dev/null || true
+  [ -n "${TMP_DIR-}" ] && rm -rf "${TMP_DIR}"
+}
+
+export NVM_DIR="$(cd ../.. && pwd)"
+
+: nvm.sh
+\. ../../nvm.sh
+
+\. ../common.sh
+
+ORIG_PWD="$(pwd)"
+
+# Run from a fresh, empty directory so no ambient .nvmrc above the test dir
+# can satisfy the lookup and mask the warning.
+TMP_DIR="$(mktemp -d)"
+cd "${TMP_DIR}" || die "could not cd to temp dir"
+
+EXEC_WARNING='WARNING: `nvm exec` was invoked without a version argument and without an .nvmrc file.'
+RUN_WARNING='WARNING: `nvm run` was invoked without a version argument and without an .nvmrc file.'
+
+for FILE in 123.js v1.23.js 1.2.3.js; do
+  set +ex # needed for stderr
+  RUN_STDERR="$(nvm run "${FILE}" </dev/null 2>&1 1>/dev/null)"
+  set -ex
+  case "${RUN_STDERR}" in
+    *"N/A: version \"v${FILE#v}\""*) die "'nvm run ${FILE}' treated the file as a version; got >${RUN_STDERR}<" ;;
+    *"${RUN_WARNING}"*) ;;
+    *) die "'nvm run ${FILE}' did not fall back with a warning; got >${RUN_STDERR}<" ;;
+  esac
+done
+
+set +ex # needed for stderr
+EXEC_STDERR="$(nvm exec 1.2.3.js </dev/null 2>&1 1>/dev/null)"
+set -ex
+case "${EXEC_STDERR}" in
+  *'N/A: version "v1.2.3.js"'*) die "'nvm exec 1.2.3.js' treated the command as a version; got >${EXEC_STDERR}<" ;;
+  *"${EXEC_WARNING}"*) ;;
+  *) die "'nvm exec 1.2.3.js' did not fall back with a warning; got >${EXEC_STDERR}<" ;;
+esac
+
+# an uninstalled prerelease is still a version, not a file
+set +ex # needed for stderr
+RUN_RC_STDERR="$(nvm run v999.0.0-rc.1 app.js </dev/null 2>&1 1>/dev/null)"
+set -ex
+case "${RUN_RC_STDERR}" in
+  *'N/A: version "v999.0.0-rc.1" is not yet installed.'*) ;;
+  *) die "'nvm run v999.0.0-rc.1' did not report the prerelease as not installed; got >${RUN_RC_STDERR}<" ;;
+esac
+
+set +ex # needed for stderr
+EXEC_RC_STDERR="$(nvm exec v999.0.0-rc.1 node </dev/null 2>&1 1>/dev/null)"
+set -ex
+case "${EXEC_RC_STDERR}" in
+  *'N/A: version "v999.0.0-rc.1" is not yet installed.'*) ;;
+  *) die "'nvm exec v999.0.0-rc.1' did not report the prerelease as not installed; got >${EXEC_RC_STDERR}<" ;;
+esac
+
+cleanup
diff --git a/test/fast/Unit tests/nvm_auto use with a prerelease default b/test/fast/Unit tests/nvm_auto use with a prerelease default
new file mode 100755
index 00000000..101d7b85
--- /dev/null
+++ b/test/fast/Unit tests/nvm_auto use with a prerelease default	
@@ -0,0 +1,39 @@
+#!/bin/sh
+
+ORIG_NVM_DIR="${NVM_DIR}"
+TMP_DIR=''
+
+cleanup () {
+  case "${TMP_DIR}" in
+    /*) rm -rf "${TMP_DIR}" ;;
+  esac
+  NVM_DIR="${ORIG_NVM_DIR}"
+  export NVM_DIR
+}
+
+die () { echo "$@" ; cleanup ; exit 1; }
+
+: nvm.sh
+\. ../../../nvm.sh
+
+\. ../../common.sh
+
+TMP_DIR="$(mktemp -d)"
+NVM_DIR="${TMP_DIR}/nvm"
+export NVM_DIR
+mkdir -p "${NVM_DIR}/alias" || die 'could not create alias dir'
+
+RELEASE='v998.0.0'
+NIGHTLY='v999.0.0-nightly20241031996708042b'
+make_fake_node "${RELEASE}" || die "fake node ${RELEASE} could not be made"
+make_fake_node "${NIGHTLY}" || die "fake node ${NIGHTLY} could not be made"
+
+for TARGET in "${NIGHTLY}" node; do
+  nvm_make_alias default "${TARGET}" || die "could not alias default to ${TARGET}"
+  nvm deactivate >/dev/null 2>&1
+  nvm_auto use || die "nvm_auto use failed with default -> ${TARGET}"
+  CURRENT="$(nvm current)"
+  [ "${CURRENT}" = "${NIGHTLY}" ] || die "with default -> ${TARGET}, nvm_auto use left 'nvm current' as >${CURRENT}<, expected >${NIGHTLY}<"
+done
+
+cleanup
diff --git a/test/fast/Unit tests/nvm_is_valid_version b/test/fast/Unit tests/nvm_is_valid_version
index 8bdf9410..8b03d14c 100755
--- a/test/fast/Unit tests/nvm_is_valid_version	
+++ b/test/fast/Unit tests/nvm_is_valid_version	
@@ -12,3 +12,32 @@ nvm_is_valid_version iojs || die "nvm_is_valid_version iojs did not return 0"
 nvm_is_valid_version node || die "nvm_is_valid_version node did not return 0"
 nvm_is_valid_version stable || die "nvm_is_valid_version stable did not return 0"
 nvm_is_valid_version unstable || die "nvm_is_valid_version unstable did not return 0"
+
+nvm_is_valid_version 123.js && die "nvm_is_valid_version 123.js did not return 1"
+nvm_is_valid_version v123.js && die "nvm_is_valid_version v123.js did not return 1"
+nvm_is_valid_version v1.js && die "nvm_is_valid_version v1.js did not return 1"
+nvm_is_valid_version v1.23.js && die "nvm_is_valid_version v1.23.js did not return 1"
+nvm_is_valid_version 1.2.3.js && die "nvm_is_valid_version 1.2.3.js did not return 1"
+nvm_is_valid_version 1.2.3.4.5.6.js && die "nvm_is_valid_version 1.2.3.4.5.6.js did not return 1"
+nvm_is_valid_version 1.2.3.4 && die "nvm_is_valid_version 1.2.3.4 did not return 1"
+nvm_is_valid_version 1..2 && die "nvm_is_valid_version 1..2 did not return 1"
+nvm_is_valid_version 1.2.3-foo.js && die "nvm_is_valid_version 1.2.3-foo.js did not return 1"
+nvm_is_valid_version 2.0.0-migration.js && die "nvm_is_valid_version 2.0.0-migration.js did not return 1"
+nvm_is_valid_version 1.2-3.4-5 && die "nvm_is_valid_version 1.2-3.4-5 did not return 1"
+nvm_is_valid_version 1.2.3- && die "nvm_is_valid_version 1.2.3- did not return 1"
+nvm_is_valid_version 1.2.3-rc..1 && die "nvm_is_valid_version 1.2.3-rc..1 did not return 1"
+nvm_is_valid_version '1.js
+2' && die "nvm_is_valid_version with an embedded newline did not return 1"
+
+nvm_is_valid_version 1 || die "nvm_is_valid_version 1 did not return 0"
+nvm_is_valid_version v1 || die "nvm_is_valid_version v1 did not return 0"
+nvm_is_valid_version 1.2 || die "nvm_is_valid_version 1.2 did not return 0"
+nvm_is_valid_version v18.20.0 || die "nvm_is_valid_version v18.20.0 did not return 0"
+nvm_is_valid_version 20. || die "nvm_is_valid_version 20. did not return 0"
+nvm_is_valid_version v18.20. || die "nvm_is_valid_version v18.20. did not return 0"
+nvm_is_valid_version iojs-v1.0.0 || die "nvm_is_valid_version iojs-v1.0.0 did not return 0"
+nvm_is_valid_version v9.4.0-rc.1 || die "nvm_is_valid_version v9.4.0-rc.1 did not return 0"
+nvm_is_valid_version v9.9.1-nightly201803256591d9f761 || die "nvm_is_valid_version v9.9.1-nightly201803256591d9f761 did not return 0"
+nvm_is_valid_version v9.0.0-v8-canary201710301f8f3dcf36 || die "nvm_is_valid_version v9.0.0-v8-canary201710301f8f3dcf36 did not return 0"
+nvm_is_valid_version v8.16.2-test201910293843c56739f || die "nvm_is_valid_version v8.16.2-test201910293843c56739f did not return 0"
+nvm_is_valid_version iojs-v3.2.1-nightly201508291a531b4e44 || die "nvm_is_valid_version iojs-v3.2.1-nightly201508291a531b4e44 did not return 0"