diff --git a/core/src/main/java/org/mapstruct/Mapping.java b/core/src/main/java/org/mapstruct/Mapping.java
index 01ffcd17a..a12aeba70 100644
--- a/core/src/main/java/org/mapstruct/Mapping.java
+++ b/core/src/main/java/org/mapstruct/Mapping.java
@@ -136,7 +136,7 @@ public @interface Mapping {
      * imported via {@link Mapper#imports()}.
      * <p>
      * This attribute can not be used together with {@link #source()}, {@link #defaultValue()},
-     * {@link #defaultExpression()} or {@link #constant()}.
+     * {@link #defaultExpression()}, {@link #qualifiedBy()}, {@link #qualifiedByName()} or {@link #constant()}.
      *
      * @return An expression specifying the value for the designated target property
      */
diff --git a/processor/src/main/java/org/mapstruct/ap/internal/model/source/Mapping.java b/processor/src/main/java/org/mapstruct/ap/internal/model/source/Mapping.java
index fabd444fc..789b22126 100644
--- a/processor/src/main/java/org/mapstruct/ap/internal/model/source/Mapping.java
+++ b/processor/src/main/java/org/mapstruct/ap/internal/model/source/Mapping.java
@@ -236,6 +236,10 @@ public class Mapping {
         else if ( mappingPrism.values.defaultValue() != null && mappingPrism.values.defaultExpression() != null ) {
             message = Message.PROPERTYMAPPING_DEFAULT_VALUE_AND_DEFAULT_EXPRESSION_BOTH_DEFINED;
         }
+        else if ( mappingPrism.values.expression() != null
+            && ( mappingPrism.values.qualifiedByName() != null || mappingPrism.values.qualifiedBy() != null ) ) {
+            message = Message.PROPERTYMAPPING_EXPRESSION_AND_QUALIFIER_BOTH_DEFINED;
+        }
         else if ( mappingPrism.values.nullValuePropertyMappingStrategy() != null
             && mappingPrism.values.defaultValue() != null ) {
             message = Message.PROPERTYMAPPING_DEFAULT_VALUE_AND_NVPMS;
diff --git a/processor/src/main/java/org/mapstruct/ap/internal/util/Message.java b/processor/src/main/java/org/mapstruct/ap/internal/util/Message.java
index 4ecf757d4..83ad59fcc 100644
--- a/processor/src/main/java/org/mapstruct/ap/internal/util/Message.java
+++ b/processor/src/main/java/org/mapstruct/ap/internal/util/Message.java
@@ -57,6 +57,7 @@ public enum Message {
     PROPERTYMAPPING_CONSTANT_VALUE_AND_NVPMS( "Constant and nullValuePropertyMappingStrategy are both defined in @Mapping, either define a constant or an nullValuePropertyMappingStrategy." ),
     PROPERTYMAPPING_DEFAULT_EXPERSSION_AND_NVPMS( "DefaultExpression and nullValuePropertyMappingStrategy are both defined in @Mapping, either define a defaultExpression or an nullValuePropertyMappingStrategy." ),
     PROPERTYMAPPING_IGNORE_AND_NVPMS( "Ignore and nullValuePropertyMappingStrategy are both defined in @Mapping, either define ignore or an nullValuePropertyMappingStrategy." ),
+    PROPERTYMAPPING_EXPRESSION_AND_QUALIFIER_BOTH_DEFINED("Expression and a qualifier both defined in @Mapping, either define an expression or a qualifier."),
     PROPERTYMAPPING_INVALID_EXPRESSION( "Value for expression must be given in the form \"java(<EXPRESSION>)\"." ),
     PROPERTYMAPPING_INVALID_DEFAULT_EXPRESSION( "Value for default expression must be given in the form \"java(<EXPRESSION>)\"." ),
     PROPERTYMAPPING_INVALID_PARAMETER_NAME( "Method has no source parameter named \"%s\". Method source parameters are: \"%s\"." ),
diff --git a/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/ErroneousSourceTargetMapperExpressionAndQualifiers.java b/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/ErroneousSourceTargetMapperExpressionAndQualifiers.java
new file mode 100644
index 000000000..189fc58b5
--- /dev/null
+++ b/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/ErroneousSourceTargetMapperExpressionAndQualifiers.java
@@ -0,0 +1,29 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.source.expressions.java;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.MappingTarget;
+import org.mapstruct.Mappings;
+import org.mapstruct.ReportingPolicy;
+
+@Mapper( uses = QualifierProvider.class, unmappedTargetPolicy = ReportingPolicy.IGNORE )
+public interface ErroneousSourceTargetMapperExpressionAndQualifiers {
+
+    @Mappings( {
+        @Mapping( target = "anotherProp", expression = "java( s.getClass().getName() )", qualifiedByName = "toUpper" ),
+        @Mapping( target = "timeAndFormat", ignore = true )
+    } )
+    Target sourceToTargetWithExpressionAndNamedQualifier(Source s, @MappingTarget Target t);
+
+    @Mappings( {
+        @Mapping( target = "anotherProp", expression = "java( s.getClass().getName() )",
+            qualifiedBy = QualifierProvider.ToUpper.class ),
+        @Mapping( target = "timeAndFormat", ignore = true )
+    } )
+    Target sourceToTargetWithExpressionAndQualifier(Source s, @MappingTarget Target t);
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/JavaExpressionTest.java b/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/JavaExpressionTest.java
index 3cec82ea9..726690ed8 100644
--- a/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/JavaExpressionTest.java
+++ b/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/JavaExpressionTest.java
@@ -17,6 +17,9 @@ import org.junit.runner.RunWith;
 import org.mapstruct.ap.test.source.expressions.java.mapper.TimeAndFormat;
 import org.mapstruct.ap.testutil.IssueKey;
 import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.CompilationResult;
+import org.mapstruct.ap.testutil.compilation.annotation.Diagnostic;
+import org.mapstruct.ap.testutil.compilation.annotation.ExpectedCompilationOutcome;
 import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
 
 /**
@@ -131,4 +134,33 @@ public class JavaExpressionTest {
         assertThat( target ).isNotNull();
         assertThat( target.getList() ).isEqualTo( Arrays.asList( "test2" ) );
     }
+
+    @IssueKey( "1851" )
+    @Test
+    @WithClasses({
+        Source.class,
+        Target.class,
+        QualifierProvider.class,
+        TimeAndFormat.class,
+        ErroneousSourceTargetMapperExpressionAndQualifiers.class
+    })
+    @ExpectedCompilationOutcome(
+        value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = ErroneousSourceTargetMapperExpressionAndQualifiers.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 18,
+                messageRegExp = "Expression and a qualifier both defined in @Mapping," +
+                    " either define an expression or a qualifier."
+            ),
+            @Diagnostic(type = ErroneousSourceTargetMapperExpressionAndQualifiers.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 24,
+                messageRegExp = "Expression and a qualifier both defined in @Mapping," +
+                    " either define an expression or a qualifier."
+            )
+        }
+    )
+    public void testExpressionAndQualifiedDoesNotCompile() {
+    }
 }
diff --git a/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/QualifierProvider.java b/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/QualifierProvider.java
new file mode 100644
index 000000000..a5a508b6f
--- /dev/null
+++ b/processor/src/test/java/org/mapstruct/ap/test/source/expressions/java/QualifierProvider.java
@@ -0,0 +1,17 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.source.expressions.java;
+
+public class QualifierProvider {
+
+    public @interface ToUpper {
+    }
+
+    @ToUpper
+    public String toUpper( String string ) {
+        return string.toUpperCase();
+    }
+}