diff --git a/env.cpp b/env.cpp
index 353085b8b..c9f986b10 100644
--- a/env.cpp
+++ b/env.cpp
@@ -542,8 +542,10 @@ void env_init(const struct config_paths_t *paths /* or NULL */)
     wcstring nshlvl_str = L"1";
     if (! shlvl_str.missing())
     {
-        long shlvl_i = wcstol(shlvl_str.c_str(), NULL, 10);
-        if (shlvl_i >= 0)
+        wchar_t *end;
+        long shlvl_i = wcstol(shlvl_str.c_str(), &end, 10);
+        while (iswspace(*end)) ++end; /* skip trailing whitespace */
+        if (shlvl_i >= 0 && *end == '\0')
         {
             nshlvl_str = to_string<long>(shlvl_i + 1);
         }
diff --git a/exec.cpp b/exec.cpp
index 3b5506da6..7706dcc50 100644
--- a/exec.cpp
+++ b/exec.cpp
@@ -651,6 +651,21 @@ void exec_job(parser_t &parser, job_t *j)
         /* PCA This is for handling exec. Passing all_ios here matches what fish 2.0.0 and 1.x did. It's known to be wrong - for example, it means that redirections bound for subsequent commands in the pipeline will apply to exec. However, using exec in a pipeline doesn't really make sense, so I'm not trying to fix it here. */
         if (!setup_child_process(j, 0, all_ios))
         {
+            /* decrement SHLVL as we're removing ourselves from the shell "stack" */
+            const env_var_t shlvl_str = env_get_string(L"SHLVL", ENV_GLOBAL | ENV_EXPORT);
+            wcstring nshlvl_str = L"0";
+            if (!shlvl_str.missing())
+            {
+                wchar_t *end;
+                long shlvl_i = wcstol(shlvl_str.c_str(), &end, 10);
+                while (iswspace(*end)) ++end; /* skip trailing whitespace */
+                if (shlvl_i > 0 && *end == '\0')
+                {
+                    nshlvl_str = to_string<long>(shlvl_i - 1);
+                }
+            }
+            env_set(L"SHLVL", nshlvl_str.c_str(), ENV_GLOBAL | ENV_EXPORT);
+
             /*
               launch_process _never_ returns
             */
diff --git a/tests/test3.in b/tests/test3.in
index 56cceeb57..b83b69c04 100644
--- a/tests/test3.in
+++ b/tests/test3.in
@@ -236,5 +236,12 @@ echo Missing: $testu
 # test SHLVL
 # use a subshell to ensure a clean slate
 env SHLVL= ../fish -c 'echo SHLVL: $SHLVL; ../fish -c \'echo SHLVL: $SHLVL\''
+# exec should decrement SHLVL
+env SHLVL= ../fish -c 'echo SHLVL: $SHLVL; exec ../fish -c \'echo SHLVL: $SHLVL\''
+# garbage SHLVLs should be treated as garbage
+env SHLVL=3foo ../fish -c 'echo SHLVL: $SHLVL'
+# whitespace is allowed though (for bash compatibility)
+env SHLVL="3  " ../fish -c 'echo SHLVL: $SHLVL'
+env SHLVL="  3" ../fish -c 'echo SHLVL: $SHLVL'
 
 true
diff --git a/tests/test3.out b/tests/test3.out
index 50563c05b..c6a21905a 100644
--- a/tests/test3.out
+++ b/tests/test3.out
@@ -23,3 +23,8 @@ Missing:
 Missing:
 SHLVL: 1
 SHLVL: 2
+SHLVL: 1
+SHLVL: 1
+SHLVL: 1
+SHLVL: 4
+SHLVL: 4