diff --git a/CHANGELOG.md b/CHANGELOG.md
index a9ea5f4..1b3a2f0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 
 ### Changed
 - SC1090: A leading `$x/` or `$(x)/` is now treated as `./` when locating files
+- SC2154: Variables appearing in -z/-n tests are no longer considered unassigned
 
 
 ## v0.7.1 - 2020-04-04
diff --git a/src/ShellCheck/Analytics.hs b/src/ShellCheck/Analytics.hs
index 40f6375..9b92698 100644
--- a/src/ShellCheck/Analytics.hs
+++ b/src/ShellCheck/Analytics.hs
@@ -2231,7 +2231,6 @@ prop_checkUnassignedReferences40= verifyNotTree checkUnassignedReferences ": ${f
 prop_checkUnassignedReferences41= verifyNotTree checkUnassignedReferences "mapfile -t files 123; echo \"${files[@]}\""
 prop_checkUnassignedReferences42= verifyNotTree checkUnassignedReferences "mapfile files -t; echo \"${files[@]}\""
 prop_checkUnassignedReferences43= verifyNotTree checkUnassignedReferences "mapfile --future files; echo \"${files[@]}\""
-
 prop_checkUnassignedReferences_minusNPlain   = verifyNotTree checkUnassignedReferences "if [ -n \"$x\" ]; then echo $x; fi"
 prop_checkUnassignedReferences_minusZPlain   = verifyNotTree checkUnassignedReferences "if [ -z \"$x\" ]; then echo \"\"; fi"
 prop_checkUnassignedReferences_minusNBraced  = verifyNotTree checkUnassignedReferences "if [ -n \"${x}\" ]; then echo $x; fi"
@@ -2239,9 +2238,6 @@ prop_checkUnassignedReferences_minusZBraced  = verifyNotTree checkUnassignedRefe
 prop_checkUnassignedReferences_minusNDefault = verifyNotTree checkUnassignedReferences "if [ -n \"${x:-}\" ]; then echo $x; fi"
 prop_checkUnassignedReferences_minusZDefault = verifyNotTree checkUnassignedReferences "if [ -z \"${x:-}\" ]; then echo \"\"; fi"
 
-prop_checkUnassignedReferences_minusZInsteadOfN       = verifyTree checkUnassignedReferences "if [ -z \"$x\" ]; then echo $x; fi"
-prop_checkUnassignedReferences_minusZInsteadOfNBraced = verifyTree checkUnassignedReferences "if [ -z \"${x}\" ]; then echo $x; fi"
-
 checkUnassignedReferences = checkUnassignedReferences' False
 checkUnassignedReferences' includeGlobals params t = warnings
   where
diff --git a/src/ShellCheck/AnalyzerLib.hs b/src/ShellCheck/AnalyzerLib.hs
index d87362c..c9954d1 100644
--- a/src/ShellCheck/AnalyzerLib.hs
+++ b/src/ShellCheck/AnalyzerLib.hs
@@ -499,8 +499,9 @@ getModifiedVariables t =
             guard . not . null $ str
             return (t, token, str, DataString SourceChecked)
 
-        TC_Unary _ _ "-n" (T_NormalWord _ [T_DoubleQuoted _ [db@(T_DollarBraced _ _ l)]]) ->
-            [(t, t, getBracedReference (concat $ oversimplify l), DataString SourceChecked)]
+        TC_Unary _ _ "-n" token -> markAsChecked t token
+        TC_Unary _ _ "-z" token -> markAsChecked t token
+        TC_Nullary _ _ token -> markAsChecked t token
 
         T_DollarBraced _ _ l -> maybeToList $ do
             let string = concat $ oversimplify l
@@ -519,6 +520,14 @@ getModifiedVariables t =
         T_ForIn id str words _ -> [(t, t, str, DataString $ SourceFrom words)]
         T_SelectIn id str words _ -> [(t, t, str, DataString $ SourceFrom words)]
         _ -> []
+  where
+    markAsChecked place token = mapMaybe (f place) $ getWordParts token
+    f place t = case t of
+            T_DollarBraced _ _ l ->
+                let str = getBracedReference $ concat $ oversimplify l in do
+                    guard $ isVariableName str
+                    return (place, t, str, DataString SourceChecked)
+            _ -> Nothing
 
 isClosingFileOp op =
     case op of
@@ -726,9 +735,7 @@ getOffsetReferences mods = fromMaybe [] $ do
 getReferencedVariables parents t =
     case t of
         T_DollarBraced id _ l -> let str = concat $ oversimplify l in
-            if isMinusZTest t
-            then []
-            else (t, t, getBracedReference str) :
+            (t, t, getBracedReference str) :
                 map (\x -> (l, l, x)) (
                     getIndexReferences str
                     ++ getOffsetReferences (getBracedModifier str))
@@ -782,10 +789,6 @@ getReferencedVariables parents t =
         this: TA_Assignment _ "=" lhs _ :_ -> lhs == t
         _                                  -> False
 
-    isMinusZTest t = case getPath parents t of
-        _ : T_DoubleQuoted _ [_] : T_NormalWord _ [_] : TC_Unary _ SingleBracket "-z" _ : _ -> True
-        _ -> False
-
 dataTypeFrom defaultType v = (case v of T_Array {} -> DataArray; _ -> defaultType) $ SourceFrom [v]