diff --git a/idea/src/org/jetbrains/kotlin/idea/inspections/NamingConventionInspections.kt b/idea/src/org/jetbrains/kotlin/idea/inspections/NamingConventionInspections.kt
index 7ac2c3cfa94..37fd18f30e7 100644
--- a/idea/src/org/jetbrains/kotlin/idea/inspections/NamingConventionInspections.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/inspections/NamingConventionInspections.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
  * that can be found in the license/LICENSE.txt file.
  */
 
@@ -48,6 +48,14 @@ private val NO_MIDDLE_UNDERSCORES = NamingRule("should not contain underscores i
     '_' in it.substring(1)
 }
 
+private val NO_BAD_CHARACTERS = NamingRule("may contain only letters and digits") {
+    it.any { c -> c !in 'a'..'z' && c !in 'A'..'Z' && c !in '0'..'9' }
+}
+
+private val NO_BAD_CHARACTERS_OR_UNDERSCORE = NamingRule("may contain only letters, digits or underscores") {
+    it.any { c -> c !in 'a'..'z' && c !in 'A'..'Z' && c !in '0'..'9' && c != '_' }
+}
+
 abstract class NamingConventionInspection(
     private val entityName: String,
     private val defaultNamePattern: String,
@@ -94,7 +102,7 @@ abstract class NamingConventionInspection(
 class ClassNameInspection : NamingConventionInspection(
     "Class",
     "[A-Z][A-Za-z\\d]*",
-    START_UPPER, NO_UNDERSCORES
+    START_UPPER, NO_UNDERSCORES, NO_BAD_CHARACTERS
 ) {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
         return object : KtVisitorVoid() {
@@ -112,7 +120,7 @@ class ClassNameInspection : NamingConventionInspection(
 class EnumEntryNameInspection : NamingConventionInspection(
     "Enum entry",
     "[A-Z]([A-Za-z\\d]*|[A-Z_\\d]*)",
-    START_UPPER
+    START_UPPER, NO_BAD_CHARACTERS_OR_UNDERSCORE
 ) {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
         return object : KtVisitorVoid() {
@@ -126,7 +134,7 @@ class EnumEntryNameInspection : NamingConventionInspection(
 class FunctionNameInspection : NamingConventionInspection(
     "Function",
     "[a-z][A-Za-z\\d]*",
-    START_LOWER, NO_UNDERSCORES
+    START_LOWER, NO_UNDERSCORES, NO_BAD_CHARACTERS
 ) {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
         return object : KtVisitorVoid() {
@@ -195,24 +203,33 @@ abstract class PropertyNameInspectionBase protected constructor(
 }
 
 class PropertyNameInspection :
-    PropertyNameInspectionBase(PropertyKind.NORMAL, "Property", "[a-z][A-Za-z\\d]*", START_LOWER, NO_UNDERSCORES)
+    PropertyNameInspectionBase(
+        PropertyKind.NORMAL, "Property", "[a-z][A-Za-z\\d]*",
+        START_LOWER, NO_UNDERSCORES, NO_BAD_CHARACTERS
+    )
 
 class ObjectPropertyNameInspection :
     PropertyNameInspectionBase(
         PropertyKind.OBJECT_OR_TOP_LEVEL,
         "Object or top-level property",
         "[A-Za-z][_A-Za-z\\d]*",
-        NO_START_UNDERSCORE
+        NO_START_UNDERSCORE, NO_BAD_CHARACTERS_OR_UNDERSCORE
     )
 
 class PrivatePropertyNameInspection :
-    PropertyNameInspectionBase(PropertyKind.PRIVATE, "Private property", "_?[a-z][A-Za-z\\d]*", NO_MIDDLE_UNDERSCORES)
+    PropertyNameInspectionBase(
+        PropertyKind.PRIVATE, "Private property", "_?[a-z][A-Za-z\\d]*",
+        NO_MIDDLE_UNDERSCORES, NO_BAD_CHARACTERS_OR_UNDERSCORE
+    )
 
 class ConstPropertyNameInspection :
     PropertyNameInspectionBase(PropertyKind.CONST, "Const property", "[A-Z][_A-Z\\d]*")
 
 class LocalVariableNameInspection :
-    PropertyNameInspectionBase(PropertyKind.LOCAL, "Local variable", "[a-z][A-Za-z\\d]*", START_LOWER, NO_UNDERSCORES)
+    PropertyNameInspectionBase(
+        PropertyKind.LOCAL, "Local variable", "[a-z][A-Za-z\\d]*",
+        START_LOWER, NO_UNDERSCORES, NO_BAD_CHARACTERS
+    )
 
 class PackageNameInspection :
     NamingConventionInspection("Package", "[a-z][A-Za-z\\d]*(\\.[a-z][A-Za-z\\d]*)*", NO_UNDERSCORES) {
diff --git a/idea/testData/inspections/naming/class/inspectionData/expected.xml b/idea/testData/inspections/naming/class/inspectionData/expected.xml
index 79b8108cf57..4b7c78fdc2e 100644
--- a/idea/testData/inspections/naming/class/inspectionData/expected.xml
+++ b/idea/testData/inspections/naming/class/inspectionData/expected.xml
@@ -21,6 +21,14 @@
         <module>light_idea_test_case</module>
         <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
         <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Class naming convention</problem_class>
-        <description>Class name &lt;code&gt;FOO_BAR&lt;/code&gt; doesn''t match regex '[A-Z][A-Za-z\d]*' #loc</description>
+        <description>Class name &lt;code&gt;FOO_BAR&lt;/code&gt; should not contain underscores #loc</description>
+    </problem>
+    <problem>
+        <file>test.kt</file>
+        <line>15</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Class naming convention</problem_class>
+        <description>Class name &lt;code&gt;`A B`&lt;/code&gt; may contain only letters and digits #loc</description>
     </problem>
 </problems>
\ No newline at end of file
diff --git a/idea/testData/inspections/naming/class/test.kt b/idea/testData/inspections/naming/class/test.kt
index bc540eca39a..a1746608694 100644
--- a/idea/testData/inspections/naming/class/test.kt
+++ b/idea/testData/inspections/naming/class/test.kt
@@ -11,3 +11,5 @@ enum class Foo {
     _Foo,
     quuxDoo,
 }
+
+class `A B`
\ No newline at end of file
diff --git a/idea/testData/inspections/naming/function/inspectionData/expected.xml b/idea/testData/inspections/naming/function/inspectionData/expected.xml
index d297390225e..494e38f73fd 100644
--- a/idea/testData/inspections/naming/function/inspectionData/expected.xml
+++ b/idea/testData/inspections/naming/function/inspectionData/expected.xml
@@ -13,4 +13,12 @@
         <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
         <description>Function name &lt;code&gt;FOO_BAR&lt;/code&gt; should not contain underscores #loc</description>
     </problem>
+    <problem>
+        <file>test.kt</file>
+        <line>7</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
+        <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Class naming convention</problem_class>
+        <description>Function name &lt;code&gt;`a b`&lt;/code&gt; may contain only letters and digits #loc</description>
+    </problem>
 </problems>
diff --git a/idea/testData/inspections/naming/function/test.kt b/idea/testData/inspections/naming/function/test.kt
index 484cec2b948..81e7dae21af 100644
--- a/idea/testData/inspections/naming/function/test.kt
+++ b/idea/testData/inspections/naming/function/test.kt
@@ -3,3 +3,5 @@ fun Foo() {}
 fun FOO_BAR() {}
 
 fun xyzzy() {}
+
+fun `a b`() {}
\ No newline at end of file