diff --git a/nvm.sh b/nvm.sh
index 5e7211f3..62cecfce 100755
--- a/nvm.sh
+++ b/nvm.sh
@@ -3247,10 +3247,11 @@ nvm_get_make_jobs() {
       NVM_CPU_CORES="$(sysctl -n hw.ncpu)"
     ;;
     "_sunos")
-      NVM_CPU_CORES="$(psrinfo | wc -l)"
+      # some `wc`s pad the count with whitespace
+      NVM_CPU_CORES="$(psrinfo | wc -l | command tr -d '[:space:]')"
     ;;
     "_aix")
-      NVM_CPU_CORES="$(pmcycles -m | wc -l)"
+      NVM_CPU_CORES="$(pmcycles -m | wc -l | command tr -d '[:space:]')"
     ;;
     *)
       # `_NPROCESSORS_ONLN` is how glibc, FreeBSD, macOS, and Cygwin spell it;
@@ -3690,6 +3691,7 @@ nvm_is_natural_num() {
   case "$1" in
     0) return 1 ;;
     -*) return 3 ;; # some BSDs return false positives for double-negated args
+    *[!0-9]*) return 2 ;; # `-eq` also accepts signs and whitespace, and in ksh, any arithmetic expression
     *)
       [ "$1" -eq "$1" ] 2>/dev/null # returns 2 if it doesn't match
     ;;
diff --git a/test/fast/Unit tests/nvm_get_make_jobs b/test/fast/Unit tests/nvm_get_make_jobs
index 481e1363..4147b0aa 100755
--- a/test/fast/Unit tests/nvm_get_make_jobs	
+++ b/test/fast/Unit tests/nvm_get_make_jobs	
@@ -132,6 +132,18 @@ run darwin
 assert_jobs 3 'darwin uses sysctl'
 assert_not_nagged 'darwin uses sysctl'
 
+# BSD-derived `wc`s right-align the count
+shim wc "echo '       4'"
+shim psrinfo 'echo 0; echo 1; echo 2; echo 3'
+run sunos
+assert_jobs 3 'sunos with a padded wc'
+assert_not_nagged 'sunos with a padded wc'
+
+shim pmcycles 'echo 0; echo 1; echo 2; echo 3'
+run aix
+assert_jobs 3 'aix with a padded wc'
+assert_not_nagged 'aix with a padded wc'
+
 export PATH="${ORIG_PATH}"
 
 # an explicit count short-circuits detection entirely
diff --git a/test/fast/Unit tests/nvm_is_natural_num b/test/fast/Unit tests/nvm_is_natural_num
index caf56cf9..b50f01b4 100755
--- a/test/fast/Unit tests/nvm_is_natural_num	
+++ b/test/fast/Unit tests/nvm_is_natural_num	
@@ -12,6 +12,12 @@ die () { echo "$@" ; exit 1; }
 ! nvm_is_natural_num --1 || 'double negative number is not false'
 ! nvm_is_natural_num 1.2 || 'decimal number is not false'
 ! nvm_is_natural_num 0 || die 'zero is not false'
+! nvm_is_natural_num +3 || die 'explicitly positive number is not false'
+! nvm_is_natural_num ' 3' || die 'leading whitespace is not false'
+! nvm_is_natural_num '3 ' || die 'trailing whitespace is not false'
+! nvm_is_natural_num install || die 'a word is not false'
+! nvm_is_natural_num V=1 || die 'an assignment is not false'
+! nvm_is_natural_num 1+1 || die 'an expression is not false'
 
 nvm_is_natural_num 1 || die '1 is not true'
 nvm_is_natural_num 2 || die '2 is not true'