diff --git a/android/rule_builder.go b/android/rule_builder.go
index 6605869..c9a9ddd 100644
--- a/android/rule_builder.go
+++ b/android/rule_builder.go
@@ -769,16 +769,25 @@
 	paths Paths
 }
 
+func checkPathNotNil(path Path) {
+	if path == nil {
+		panic("rule_builder paths cannot be nil")
+	}
+}
+
 func (c *RuleBuilderCommand) addInput(path Path) string {
+	checkPathNotNil(path)
 	c.inputs = append(c.inputs, path)
 	return c.PathForInput(path)
 }
 
 func (c *RuleBuilderCommand) addImplicit(path Path) {
+	checkPathNotNil(path)
 	c.implicits = append(c.implicits, path)
 }
 
 func (c *RuleBuilderCommand) addOrderOnly(path Path) {
+	checkPathNotNil(path)
 	c.orderOnlys = append(c.orderOnlys, path)
 }
 
@@ -1004,19 +1013,23 @@
 // Tool adds the specified tool path to the command line.  The path will be also added to the dependencies returned by
 // RuleBuilder.Tools.
 func (c *RuleBuilderCommand) Tool(path Path) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.tools = append(c.tools, path)
 	return c.Text(c.PathForTool(path))
 }
 
 // Tool adds the specified tool path to the dependencies returned by RuleBuilder.Tools.
 func (c *RuleBuilderCommand) ImplicitTool(path Path) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.tools = append(c.tools, path)
 	return c
 }
 
 // Tool adds the specified tool path to the dependencies returned by RuleBuilder.Tools.
 func (c *RuleBuilderCommand) ImplicitTools(paths Paths) *RuleBuilderCommand {
-	c.tools = append(c.tools, paths...)
+	for _, path := range paths {
+		c.ImplicitTool(path)
+	}
 	return c
 }
 
@@ -1093,6 +1106,7 @@
 // Validation adds the specified input path to the validation dependencies by
 // RuleBuilder.Validations without modifying the command line.
 func (c *RuleBuilderCommand) Validation(path Path) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.validations = append(c.validations, path)
 	return c
 }
@@ -1100,13 +1114,16 @@
 // Validations adds the specified input paths to the validation dependencies by
 // RuleBuilder.Validations without modifying the command line.
 func (c *RuleBuilderCommand) Validations(paths Paths) *RuleBuilderCommand {
-	c.validations = append(c.validations, paths...)
+	for _, path := range paths {
+		c.Validation(path)
+	}
 	return c
 }
 
 // Output adds the specified output path to the command line.  The path will also be added to the outputs returned by
 // RuleBuilder.Outputs.
 func (c *RuleBuilderCommand) Output(path WritablePath) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.outputs = append(c.outputs, path)
 	return c.Text(c.PathForOutput(path))
 }
@@ -1133,6 +1150,7 @@
 // line, and causes RuleBuilder.Build file to set the depfile flag for ninja.  If multiple depfiles are added to
 // commands in a single RuleBuilder then RuleBuilder.Build will add an extra command to merge the depfiles together.
 func (c *RuleBuilderCommand) DepFile(path WritablePath) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.depFiles = append(c.depFiles, path)
 	return c.Text(c.PathForOutput(path))
 }
@@ -1155,6 +1173,7 @@
 // will be a symlink instead of a regular file. Does not modify the command
 // line.
 func (c *RuleBuilderCommand) ImplicitSymlinkOutput(path WritablePath) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.symlinkOutputs = append(c.symlinkOutputs, path)
 	return c.ImplicitOutput(path)
 }
@@ -1172,6 +1191,7 @@
 // SymlinkOutput declares the specified path as an output that will be a symlink
 // instead of a regular file. Modifies the command line.
 func (c *RuleBuilderCommand) SymlinkOutput(path WritablePath) *RuleBuilderCommand {
+	checkPathNotNil(path)
 	c.symlinkOutputs = append(c.symlinkOutputs, path)
 	return c.Output(path)
 }