diff --git a/package.json b/package.json
index 42a1948..2c89d68 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
   "types": "lib/index.d.ts",
   "scripts": {
     "test": "tsc -p ./tsconfig.cjs.json --noEmit && jest",
-    "lint": "tslint --project tsconfig.base.json",
+    "lint": "tslint --project tsconfig.json",
     "format": "prettier --write \"src/**/*.ts\"",
     "test:watch": "jest --watch",
     "build": "rimraf ./lib && rimraf ./es && tsc -p ./tsconfig.cjs.json && tsc -p ./tsconfig.esm.json",
diff --git a/src/__tests__/style.ts b/src/__tests__/style.ts
index 10bf6f5..a7a1fd8 100644
--- a/src/__tests__/style.ts
+++ b/src/__tests__/style.ts
@@ -64,9 +64,7 @@ describe('style', () => {
   });
 
   it('should return `undefined` if specified prop is not set', () => {
-    const result = style<IProps>({ cssProp: 'output', prop: 'input' })({
-      theme: {},
-    });
+    const result = style<IProps>({ cssProp: 'output', prop: 'input' })({});
 
     expect(result).toBe(undefined);
   });
@@ -74,7 +72,6 @@ describe('style', () => {
   it('should assign the value of `prop` to `cssProp` and return an object if a value is set', () => {
     const result = style<IProps>({ cssProp: 'output', prop: 'input' })({
       input: 'value',
-      theme: {},
     });
 
     expect(result).toEqual({ output: 'value' });
@@ -129,8 +126,8 @@ describe('style', () => {
   it('should return the respective values for breakpoints', () => {
     const result = style<
       IColorProps<typeof theme.colors>,
-      ITheme,
-      IBreakpoints
+      typeof themeWithBreakpoints,
+      typeof themeWithBreakpoints.breakpoints
     >({
       cssProp: 'color',
       prop: 'input',
@@ -160,8 +157,8 @@ describe('style', () => {
   it('should return the value as is for each breakpoint, if no value can be found on the theme', () => {
     const result = style<
       IColorProps<{ [index: string]: string }>,
-      ITheme,
-      IBreakpoints
+      typeof themeWithBreakpoints,
+      typeof themeWithBreakpoints.breakpoints
     >({
       cssProp: 'color',
       prop: 'input',
@@ -191,8 +188,8 @@ describe('style', () => {
   it('should order media query results based on ordering within `theme.breakpoints` not based on ordering of the responsive object props', () => {
     const result = style<
       IColorProps<{ [index: string]: string }>,
-      ITheme,
-      IBreakpoints
+      typeof themeWithBreakpoints,
+      typeof themeWithBreakpoints.breakpoints
     >({
       cssProp: 'color',
       prop: 'input',
@@ -218,8 +215,8 @@ describe('style', () => {
   it('should allow `base` as value for breakpoints to define the base value (without media query) of a property', () => {
     const result = style<
       IColorProps<typeof theme.colors>,
-      ITheme,
-      IBreakpoints
+      typeof themeWithBreakpoints,
+      typeof themeWithBreakpoints.breakpoints
     >({
       cssProp: 'color',
       prop: 'input',
@@ -251,8 +248,8 @@ describe('style', () => {
   it('should put base values in front of all other values', () => {
     const result = style<
       IColorProps<typeof theme.colors>,
-      ITheme,
-      IBreakpoints
+      typeof themeWithBreakpoints,
+      typeof themeWithBreakpoints.breakpoints
     >({
       cssProp: 'color',
       prop: 'input',
@@ -274,4 +271,39 @@ describe('style', () => {
       themeWithBreakpoints.breakpoints.large,
     ]);
   });
+
+  it('should return `undefined` if a responsive object is passed in but no theme and/or breakpoints are provided', () => {
+    const func = style<
+      IColorProps<typeof theme.colors>,
+      typeof themeWithBreakpoints,
+      typeof themeWithBreakpoints.breakpoints
+    >({
+      cssProp: 'color',
+      prop: 'input',
+      themeProp: 'colors',
+    });
+
+    const noThemeResult = func({
+      input: {
+        base: 'red',
+        large: 'red',
+        medium: 'green',
+        small: 'blue',
+      },
+      theme: null as typeof themeWithBreakpoints,
+    });
+
+    const noBreakpointsResult = func({
+      input: {
+        base: 'red',
+        large: 'red',
+        medium: 'green',
+        small: 'blue',
+      },
+      theme: {} as typeof themeWithBreakpoints,
+    });
+
+    expect(noThemeResult).toBe(undefined);
+    expect(noBreakpointsResult).toBe(undefined);
+  });
 });
diff --git a/src/style.ts b/src/style.ts
index 146a288..7a2069a 100644
--- a/src/style.ts
+++ b/src/style.ts
@@ -1,14 +1,16 @@
 import {
+  IDictionary,
   IStyleOptions,
   IStyles,
   ResponsivePropValue,
   WithTheme,
 } from './types';
 
-const BASE_EMPTY_OBJECT: { [index: string]: string } = {};
+const BASE_EMPTY_OBJECT = {};
+const BASE_EMPTY_INDEXED_OBJECT: IDictionary<any> = BASE_EMPTY_OBJECT;
 const BREAKPOINTS_BASE_VALUE_KEY = 'base';
 
-export function style<P, T = {}, B = never>({
+export function style<P, T extends {} = never, B extends {} = never>({
   cssProp,
   prop,
   themeProp,
@@ -20,9 +22,11 @@ export function style<P, T = {}, B = never>({
       return undefined;
     }
 
-    const themeValue = themeProp
-      ? (props.theme[themeProp] as { [index: string]: any })
-      : undefined;
+    const themeValue =
+      themeProp && props.theme
+        ? (props.theme[themeProp] as { [index: string]: any })
+        : undefined;
+
     const finalValue =
       themeValue &&
       (typeof propValue === 'string' || typeof propValue === 'number') &&
@@ -34,11 +38,12 @@ export function style<P, T = {}, B = never>({
       return {
         [cssProp]: finalValue,
       };
+    } else if (!props.theme || !props.theme.breakpoints) {
+      return undefined;
     } else {
       const result: IStyles = {};
-      const { theme } = props;
-      const { breakpoints = BASE_EMPTY_OBJECT } = theme;
-      const themeVal = themeValue || BASE_EMPTY_OBJECT;
+      const { breakpoints } = props.theme;
+      const themeVal = themeValue || BASE_EMPTY_INDEXED_OBJECT;
       // We rely on the fact that `Object.keys` enumerates keys in the way
       // they are added to an object. This should be consistent across engines.
       // In case that a bug is discovered we will have to switch to an implicit
@@ -62,8 +67,9 @@ export function style<P, T = {}, B = never>({
           if (key === BREAKPOINTS_BASE_VALUE_KEY) {
             acc[cssProp] = val;
           } else {
-            // TODO how to get around the cast to any?
-            const breakpointValue: string = breakpoints[key] as any;
+            const breakpointValue: string = (breakpoints as IDictionary<any>)[
+              key.toString()
+            ];
             acc[breakpointValue] = {
               [cssProp]: val,
             };
diff --git a/src/types.ts b/src/types.ts
index 433fe93..2ee0041 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -20,6 +20,10 @@ export type ResponsiveProp<ValueType, BreakPoints = never> = [
   ? ValueType
   : ValueType | ResponsivePropValue<BreakPoints, ValueType>;
 
+export interface IDictionary<T> {
+  [index: string]: T;
+}
+
 export type ResponsiveObject<P, B> = {
   [K in keyof P]?: ResponsiveProp<P[K], B>
 };
@@ -33,7 +37,7 @@ export interface IBreakpointTheme<T, B> {
 }
 
 export type ThemeWithBreakpoints<T, B> = [B] extends [never]
-  ? ITheme<T>
+  ? [T] extends [never] ? Partial<ITheme<T>> : ITheme<T>
   : IBreakpointTheme<T, B>;
 
 export type WithTheme<P, T, B> = ResponsiveObject<P, B> &
diff --git a/tsconfig.cjs.json b/tsconfig.cjs.json
index 74089b3..81df269 100644
--- a/tsconfig.cjs.json
+++ b/tsconfig.cjs.json
@@ -1,5 +1,5 @@
 {
-  "extends": "./tsconfig.base.json",
+  "extends": "./tsconfig.json",
   "compilerOptions": {
     "module": "commonjs",
     "outDir": "lib"
diff --git a/tsconfig.esm.json b/tsconfig.esm.json
index 8e2be10..b5cc877 100644
--- a/tsconfig.esm.json
+++ b/tsconfig.esm.json
@@ -1,5 +1,5 @@
 {
-  "extends": "./tsconfig.base.json",
+  "extends": "./tsconfig.json",
   "compilerOptions": {
     "module": "esnext",
     "outDir": "es"
diff --git a/tsconfig.base.json b/tsconfig.json
similarity index 100%
rename from tsconfig.base.json
rename to tsconfig.json